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6412 lines
225 KiB
6412 lines
225 KiB
acpi= [HW,ACPI,X86,ARM64] |
|
Advanced Configuration and Power Interface |
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Format: { force | on | off | strict | noirq | rsdt | |
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copy_dsdt } |
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force -- enable ACPI if default was off |
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on -- enable ACPI but allow fallback to DT [arm64] |
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off -- disable ACPI if default was on |
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noirq -- do not use ACPI for IRQ routing |
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strict -- Be less tolerant of platforms that are not |
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strictly ACPI specification compliant. |
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rsdt -- prefer RSDT over (default) XSDT |
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copy_dsdt -- copy DSDT to memory |
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For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" |
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are available |
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|
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See also Documentation/power/runtime_pm.rst, pci=noacpi |
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|
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acpi_apic_instance= [ACPI, IOAPIC] |
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Format: <int> |
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2: use 2nd APIC table, if available |
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1,0: use 1st APIC table |
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default: 0 |
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|
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acpi_backlight= [HW,ACPI] |
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{ vendor | video | native | none } |
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If set to vendor, prefer vendor-specific driver |
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(e.g. thinkpad_acpi, sony_acpi, etc.) instead |
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of the ACPI video.ko driver. |
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If set to video, use the ACPI video.ko driver. |
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If set to native, use the device's native backlight mode. |
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If set to none, disable the ACPI backlight interface. |
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|
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acpi_force_32bit_fadt_addr |
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force FADT to use 32 bit addresses rather than the |
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64 bit X_* addresses. Some firmware have broken 64 |
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bit addresses for force ACPI ignore these and use |
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the older legacy 32 bit addresses. |
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|
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acpica_no_return_repair [HW, ACPI] |
|
Disable AML predefined validation mechanism |
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This mechanism can repair the evaluation result to make |
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the return objects more ACPI specification compliant. |
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This option is useful for developers to identify the |
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root cause of an AML interpreter issue when the issue |
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has something to do with the repair mechanism. |
|
|
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acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] |
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acpi.debug_level= [HW,ACPI,ACPI_DEBUG] |
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Format: <int> |
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CONFIG_ACPI_DEBUG must be enabled to produce any ACPI |
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debug output. Bits in debug_layer correspond to a |
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_COMPONENT in an ACPI source file, e.g., |
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#define _COMPONENT ACPI_EVENTS |
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Bits in debug_level correspond to a level in |
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ACPI_DEBUG_PRINT statements, e.g., |
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ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... |
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The debug_level mask defaults to "info". See |
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Documentation/firmware-guide/acpi/debug.rst for more information about |
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debug layers and levels. |
|
|
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Enable processor driver info messages: |
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acpi.debug_layer=0x20000000 |
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Enable AML "Debug" output, i.e., stores to the Debug |
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object while interpreting AML: |
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acpi.debug_layer=0xffffffff acpi.debug_level=0x2 |
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Enable all messages related to ACPI hardware: |
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acpi.debug_layer=0x2 acpi.debug_level=0xffffffff |
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|
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Some values produce so much output that the system is |
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unusable. The "log_buf_len" parameter may be useful |
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if you need to capture more output. |
|
|
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acpi_enforce_resources= [ACPI] |
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{ strict | lax | no } |
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Check for resource conflicts between native drivers |
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and ACPI OperationRegions (SystemIO and SystemMemory |
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only). IO ports and memory declared in ACPI might be |
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used by the ACPI subsystem in arbitrary AML code and |
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can interfere with legacy drivers. |
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strict (default): access to resources claimed by ACPI |
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is denied; legacy drivers trying to access reserved |
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resources will fail to bind to device using them. |
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lax: access to resources claimed by ACPI is allowed; |
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legacy drivers trying to access reserved resources |
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will bind successfully but a warning message is logged. |
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no: ACPI OperationRegions are not marked as reserved, |
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no further checks are performed. |
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|
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acpi_force_table_verification [HW,ACPI] |
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Enable table checksum verification during early stage. |
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By default, this is disabled due to x86 early mapping |
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size limitation. |
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|
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acpi_irq_balance [HW,ACPI] |
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ACPI will balance active IRQs |
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default in APIC mode |
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|
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acpi_irq_nobalance [HW,ACPI] |
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ACPI will not move active IRQs (default) |
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default in PIC mode |
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|
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acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA |
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Format: <irq>,<irq>... |
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|
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acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for |
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use by PCI |
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Format: <irq>,<irq>... |
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|
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acpi_mask_gpe= [HW,ACPI] |
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Due to the existence of _Lxx/_Exx, some GPEs triggered |
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by unsupported hardware/firmware features can result in |
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GPE floodings that cannot be automatically disabled by |
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the GPE dispatcher. |
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This facility can be used to prevent such uncontrolled |
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GPE floodings. |
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Format: <byte> or <bitmap-list> |
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|
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acpi_no_auto_serialize [HW,ACPI] |
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Disable auto-serialization of AML methods |
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AML control methods that contain the opcodes to create |
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named objects will be marked as "Serialized" by the |
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auto-serialization feature. |
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This feature is enabled by default. |
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This option allows to turn off the feature. |
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|
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acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump |
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kernels. |
|
|
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acpi_no_static_ssdt [HW,ACPI] |
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Disable installation of static SSDTs at early boot time |
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By default, SSDTs contained in the RSDT/XSDT will be |
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installed automatically and they will appear under |
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/sys/firmware/acpi/tables. |
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This option turns off this feature. |
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Note that specifying this option does not affect |
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dynamic table installation which will install SSDT |
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tables to /sys/firmware/acpi/tables/dynamic. |
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|
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acpi_no_watchdog [HW,ACPI,WDT] |
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Ignore the ACPI-based watchdog interface (WDAT) and let |
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a native driver control the watchdog device instead. |
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|
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acpi_rsdp= [ACPI,EFI,KEXEC] |
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Pass the RSDP address to the kernel, mostly used |
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on machines running EFI runtime service to boot the |
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second kernel for kdump. |
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|
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acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS |
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Format: To spoof as Windows 98: ="Microsoft Windows" |
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|
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acpi_rev_override [ACPI] Override the _REV object to return 5 (instead |
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of 2 which is mandated by ACPI 6) as the supported ACPI |
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specification revision (when using this switch, it may |
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be necessary to carry out a cold reboot _twice_ in a |
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row to make it take effect on the platform firmware). |
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|
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acpi_osi= [HW,ACPI] Modify list of supported OS interface strings |
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acpi_osi="string1" # add string1 |
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acpi_osi="!string2" # remove string2 |
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acpi_osi=!* # remove all strings |
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acpi_osi=! # disable all built-in OS vendor |
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strings |
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acpi_osi=!! # enable all built-in OS vendor |
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strings |
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acpi_osi= # disable all strings |
|
|
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'acpi_osi=!' can be used in combination with single or |
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multiple 'acpi_osi="string1"' to support specific OS |
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vendor string(s). Note that such command can only |
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affect the default state of the OS vendor strings, thus |
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it cannot affect the default state of the feature group |
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strings and the current state of the OS vendor strings, |
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specifying it multiple times through kernel command line |
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is meaningless. This command is useful when one do not |
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care about the state of the feature group strings which |
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should be controlled by the OSPM. |
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Examples: |
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1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent |
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to 'acpi_osi="Windows 2000" acpi_osi=!', they all |
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can make '_OSI("Windows 2000")' TRUE. |
|
|
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'acpi_osi=' cannot be used in combination with other |
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'acpi_osi=' command lines, the _OSI method will not |
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exist in the ACPI namespace. NOTE that such command can |
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only affect the _OSI support state, thus specifying it |
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multiple times through kernel command line is also |
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meaningless. |
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Examples: |
|
1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' |
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FALSE. |
|
|
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'acpi_osi=!*' can be used in combination with single or |
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multiple 'acpi_osi="string1"' to support specific |
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string(s). Note that such command can affect the |
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current state of both the OS vendor strings and the |
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feature group strings, thus specifying it multiple times |
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through kernel command line is meaningful. But it may |
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still not able to affect the final state of a string if |
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there are quirks related to this string. This command |
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is useful when one want to control the state of the |
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feature group strings to debug BIOS issues related to |
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the OSPM features. |
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Examples: |
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1. 'acpi_osi="Module Device" acpi_osi=!*' can make |
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'_OSI("Module Device")' FALSE. |
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2. 'acpi_osi=!* acpi_osi="Module Device"' can make |
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'_OSI("Module Device")' TRUE. |
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3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is |
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equivalent to |
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'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' |
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and |
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'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', |
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they all will make '_OSI("Windows 2000")' TRUE. |
|
|
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acpi_pm_good [X86] |
|
Override the pmtimer bug detection: force the kernel |
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to assume that this machine's pmtimer latches its value |
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and always returns good values. |
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|
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acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode |
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Format: { level | edge | high | low } |
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|
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acpi_skip_timer_override [HW,ACPI] |
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Recognize and ignore IRQ0/pin2 Interrupt Override. |
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For broken nForce2 BIOS resulting in XT-PIC timer. |
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|
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acpi_sleep= [HW,ACPI] Sleep options |
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Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, |
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old_ordering, nonvs, sci_force_enable, nobl } |
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See Documentation/power/video.rst for information on |
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s3_bios and s3_mode. |
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s3_beep is for debugging; it makes the PC's speaker beep |
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as soon as the kernel's real-mode entry point is called. |
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s4_nohwsig prevents ACPI hardware signature from being |
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used during resume from hibernation. |
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old_ordering causes the ACPI 1.0 ordering of the _PTS |
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control method, with respect to putting devices into |
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low power states, to be enforced (the ACPI 2.0 ordering |
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of _PTS is used by default). |
|
nonvs prevents the kernel from saving/restoring the |
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ACPI NVS memory during suspend/hibernation and resume. |
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sci_force_enable causes the kernel to set SCI_EN directly |
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on resume from S1/S3 (which is against the ACPI spec, |
|
but some broken systems don't work without it). |
|
nobl causes the internal blacklist of systems known to |
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behave incorrectly in some ways with respect to system |
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suspend and resume to be ignored (use wisely). |
|
|
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acpi_use_timer_override [HW,ACPI] |
|
Use timer override. For some broken Nvidia NF5 boards |
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that require a timer override, but don't have HPET |
|
|
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add_efi_memmap [EFI; X86] Include EFI memory map in |
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kernel's map of available physical RAM. |
|
|
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agp= [AGP] |
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{ off | try_unsupported } |
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off: disable AGP support |
|
try_unsupported: try to drive unsupported chipsets |
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(may crash computer or cause data corruption) |
|
|
|
ALSA [HW,ALSA] |
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See Documentation/sound/alsa-configuration.rst |
|
|
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alignment= [KNL,ARM] |
|
Allow the default userspace alignment fault handler |
|
behaviour to be specified. Bit 0 enables warnings, |
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bit 1 enables fixups, and bit 2 sends a segfault. |
|
|
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align_va_addr= [X86-64] |
|
Align virtual addresses by clearing slice [14:12] when |
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allocating a VMA at process creation time. This option |
|
gives you up to 3% performance improvement on AMD F15h |
|
machines (where it is enabled by default) for a |
|
CPU-intensive style benchmark, and it can vary highly in |
|
a microbenchmark depending on workload and compiler. |
|
|
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32: only for 32-bit processes |
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64: only for 64-bit processes |
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on: enable for both 32- and 64-bit processes |
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off: disable for both 32- and 64-bit processes |
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|
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alloc_snapshot [FTRACE] |
|
Allocate the ftrace snapshot buffer on boot up when the |
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main buffer is allocated. This is handy if debugging |
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and you need to use tracing_snapshot() on boot up, and |
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do not want to use tracing_snapshot_alloc() as it needs |
|
to be done where GFP_KERNEL allocations are allowed. |
|
|
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allow_mismatched_32bit_el0 [ARM64] |
|
Allow execve() of 32-bit applications and setting of the |
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PER_LINUX32 personality on systems where only a strict |
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subset of the CPUs support 32-bit EL0. When this |
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parameter is present, the set of CPUs supporting 32-bit |
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EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 |
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and hot-unplug operations may be restricted. |
|
|
|
See Documentation/arm64/asymmetric-32bit.rst for more |
|
information. |
|
|
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amd_iommu= [HW,X86-64] |
|
Pass parameters to the AMD IOMMU driver in the system. |
|
Possible values are: |
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fullflush - Deprecated, equivalent to iommu.strict=1 |
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off - do not initialize any AMD IOMMU found in |
|
the system |
|
force_isolation - Force device isolation for all |
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devices. The IOMMU driver is not |
|
allowed anymore to lift isolation |
|
requirements as needed. This option |
|
does not override iommu=pt |
|
force_enable - Force enable the IOMMU on platforms known |
|
to be buggy with IOMMU enabled. Use this |
|
option with care. |
|
|
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amd_iommu_dump= [HW,X86-64] |
|
Enable AMD IOMMU driver option to dump the ACPI table |
|
for AMD IOMMU. With this option enabled, AMD IOMMU |
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driver will print ACPI tables for AMD IOMMU during |
|
IOMMU initialization. |
|
|
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amd_iommu_intr= [HW,X86-64] |
|
Specifies one of the following AMD IOMMU interrupt |
|
remapping modes: |
|
legacy - Use legacy interrupt remapping mode. |
|
vapic - Use virtual APIC mode, which allows IOMMU |
|
to inject interrupts directly into guest. |
|
This mode requires kvm-amd.avic=1. |
|
(Default when IOMMU HW support is present.) |
|
|
|
amijoy.map= [HW,JOY] Amiga joystick support |
|
Map of devices attached to JOY0DAT and JOY1DAT |
|
Format: <a>,<b> |
|
See also Documentation/input/joydev/joystick.rst |
|
|
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analog.map= [HW,JOY] Analog joystick and gamepad support |
|
Specifies type or capabilities of an analog joystick |
|
connected to one of 16 gameports |
|
Format: <type1>,<type2>,..<type16> |
|
|
|
apc= [HW,SPARC] |
|
Power management functions (SPARCstation-4/5 + deriv.) |
|
Format: noidle |
|
Disable APC CPU standby support. SPARCstation-Fox does |
|
not play well with APC CPU idle - disable it if you have |
|
APC and your system crashes randomly. |
|
|
|
apic= [APIC,X86] Advanced Programmable Interrupt Controller |
|
Change the output verbosity while booting |
|
Format: { quiet (default) | verbose | debug } |
|
Change the amount of debugging information output |
|
when initialising the APIC and IO-APIC components. |
|
For X86-32, this can also be used to specify an APIC |
|
driver name. |
|
Format: apic=driver_name |
|
Examples: apic=bigsmp |
|
|
|
apic_extnmi= [APIC,X86] External NMI delivery setting |
|
Format: { bsp (default) | all | none } |
|
bsp: External NMI is delivered only to CPU 0 |
|
all: External NMIs are broadcast to all CPUs as a |
|
backup of CPU 0 |
|
none: External NMI is masked for all CPUs. This is |
|
useful so that a dump capture kernel won't be |
|
shot down by NMI |
|
|
|
autoconf= [IPV6] |
|
See Documentation/networking/ipv6.rst. |
|
|
|
show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
|
Limit apic dumping. The parameter defines the maximal |
|
number of local apics being dumped. Also it is possible |
|
to set it to "all" by meaning -- no limit here. |
|
Format: { 1 (default) | 2 | ... | all }. |
|
The parameter valid if only apic=debug or |
|
apic=verbose is specified. |
|
Example: apic=debug show_lapic=all |
|
|
|
apm= [APM] Advanced Power Management |
|
See header of arch/x86/kernel/apm_32.c. |
|
|
|
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
|
Format: <io>,<irq>,<nodeID> |
|
|
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arm64.nobti [ARM64] Unconditionally disable Branch Target |
|
Identification support |
|
|
|
arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication |
|
support |
|
|
|
arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension |
|
support |
|
|
|
ataflop= [HW,M68k] |
|
|
|
atarimouse= [HW,MOUSE] Atari Mouse |
|
|
|
atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
|
EzKey and similar keyboards |
|
|
|
atkbd.reset= [HW] Reset keyboard during initialization |
|
|
|
atkbd.set= [HW] Select keyboard code set |
|
Format: <int> (2 = AT (default), 3 = PS/2) |
|
|
|
atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar |
|
keyboards |
|
|
|
atkbd.softraw= [HW] Choose between synthetic and real raw mode |
|
Format: <bool> (0 = real, 1 = synthetic (default)) |
|
|
|
atkbd.softrepeat= [HW] |
|
Use software keyboard repeat |
|
|
|
audit= [KNL] Enable the audit sub-system |
|
Format: { "0" | "1" | "off" | "on" } |
|
0 | off - kernel audit is disabled and can not be |
|
enabled until the next reboot |
|
unset - kernel audit is initialized but disabled and |
|
will be fully enabled by the userspace auditd. |
|
1 | on - kernel audit is initialized and partially |
|
enabled, storing at most audit_backlog_limit |
|
messages in RAM until it is fully enabled by the |
|
userspace auditd. |
|
Default: unset |
|
|
|
audit_backlog_limit= [KNL] Set the audit queue size limit. |
|
Format: <int> (must be >=0) |
|
Default: 64 |
|
|
|
bau= [X86_UV] Enable the BAU on SGI UV. The default |
|
behavior is to disable the BAU (i.e. bau=0). |
|
Format: { "0" | "1" } |
|
0 - Disable the BAU. |
|
1 - Enable the BAU. |
|
unset - Disable the BAU. |
|
|
|
baycom_epp= [HW,AX25] |
|
Format: <io>,<mode> |
|
|
|
baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem |
|
Format: <io>,<mode> |
|
See header of drivers/net/hamradio/baycom_par.c. |
|
|
|
baycom_ser_fdx= [HW,AX25] |
|
BayCom Serial Port AX.25 Modem (Full Duplex Mode) |
|
Format: <io>,<irq>,<mode>[,<baud>] |
|
See header of drivers/net/hamradio/baycom_ser_fdx.c. |
|
|
|
baycom_ser_hdx= [HW,AX25] |
|
BayCom Serial Port AX.25 Modem (Half Duplex Mode) |
|
Format: <io>,<irq>,<mode> |
|
See header of drivers/net/hamradio/baycom_ser_hdx.c. |
|
|
|
blkdevparts= Manual partition parsing of block device(s) for |
|
embedded devices based on command line input. |
|
See Documentation/block/cmdline-partition.rst |
|
|
|
boot_delay= Milliseconds to delay each printk during boot. |
|
Values larger than 10 seconds (10000) are changed to |
|
no delay (0). |
|
Format: integer |
|
|
|
bootconfig [KNL] |
|
Extended command line options can be added to an initrd |
|
and this will cause the kernel to look for it. |
|
|
|
See Documentation/admin-guide/bootconfig.rst |
|
|
|
bert_disable [ACPI] |
|
Disable BERT OS support on buggy BIOSes. |
|
|
|
bgrt_disable [ACPI][X86] |
|
Disable BGRT to avoid flickering OEM logo. |
|
|
|
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) |
|
bttv.radio= Most important insmod options are available as |
|
kernel args too. |
|
bttv.pll= See Documentation/admin-guide/media/bttv.rst |
|
bttv.tuner= |
|
|
|
bulk_remove=off [PPC] This parameter disables the use of the pSeries |
|
firmware feature for flushing multiple hpte entries |
|
at a time. |
|
|
|
c101= [NET] Moxa C101 synchronous serial card |
|
|
|
cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. |
|
Sometimes CPU hardware bugs make them report the cache |
|
size incorrectly. The kernel will attempt work arounds |
|
to fix known problems, but for some CPUs it is not |
|
possible to determine what the correct size should be. |
|
This option provides an override for these situations. |
|
|
|
carrier_timeout= |
|
[NET] Specifies amount of time (in seconds) that |
|
the kernel should wait for a network carrier. By default |
|
it waits 120 seconds. |
|
|
|
ca_keys= [KEYS] This parameter identifies a specific key(s) on |
|
the system trusted keyring to be used for certificate |
|
trust validation. |
|
format: { id:<keyid> | builtin } |
|
|
|
cca= [MIPS] Override the kernel pages' cache coherency |
|
algorithm. Accepted values range from 0 to 7 |
|
inclusive. See arch/mips/include/asm/pgtable-bits.h |
|
for platform specific values (SB1, Loongson3 and |
|
others). |
|
|
|
ccw_timeout_log [S390] |
|
See Documentation/s390/common_io.rst for details. |
|
|
|
cgroup_disable= [KNL] Disable a particular controller or optional feature |
|
Format: {name of the controller(s) or feature(s) to disable} |
|
The effects of cgroup_disable=foo are: |
|
- foo isn't auto-mounted if you mount all cgroups in |
|
a single hierarchy |
|
- foo isn't visible as an individually mountable |
|
subsystem |
|
- if foo is an optional feature then the feature is |
|
disabled and corresponding cgroup files are not |
|
created |
|
{Currently only "memory" controller deal with this and |
|
cut the overhead, others just disable the usage. So |
|
only cgroup_disable=memory is actually worthy} |
|
Specifying "pressure" disables per-cgroup pressure |
|
stall information accounting feature |
|
|
|
cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 |
|
Format: { { controller | "all" | "named" } |
|
[,{ controller | "all" | "named" }...] } |
|
Like cgroup_disable, but only applies to cgroup v1; |
|
the blacklisted controllers remain available in cgroup2. |
|
"all" blacklists all controllers and "named" disables |
|
named mounts. Specifying both "all" and "named" disables |
|
all v1 hierarchies. |
|
|
|
cgroup.memory= [KNL] Pass options to the cgroup memory controller. |
|
Format: <string> |
|
nosocket -- Disable socket memory accounting. |
|
nokmem -- Disable kernel memory accounting. |
|
|
|
checkreqprot [SELINUX] Set initial checkreqprot flag value. |
|
Format: { "0" | "1" } |
|
See security/selinux/Kconfig help text. |
|
0 -- check protection applied by kernel (includes |
|
any implied execute protection). |
|
1 -- check protection requested by application. |
|
Default value is set via a kernel config option. |
|
Value can be changed at runtime via |
|
/sys/fs/selinux/checkreqprot. |
|
Setting checkreqprot to 1 is deprecated. |
|
|
|
cio_ignore= [S390] |
|
See Documentation/s390/common_io.rst for details. |
|
clk_ignore_unused |
|
[CLK] |
|
Prevents the clock framework from automatically gating |
|
clocks that have not been explicitly enabled by a Linux |
|
device driver but are enabled in hardware at reset or |
|
by the bootloader/firmware. Note that this does not |
|
force such clocks to be always-on nor does it reserve |
|
those clocks in any way. This parameter is useful for |
|
debug and development, but should not be needed on a |
|
platform with proper driver support. For more |
|
information, see Documentation/driver-api/clk.rst. |
|
|
|
clock= [BUGS=X86-32, HW] gettimeofday clocksource override. |
|
[Deprecated] |
|
Forces specified clocksource (if available) to be used |
|
when calculating gettimeofday(). If specified |
|
clocksource is not available, it defaults to PIT. |
|
Format: { pit | tsc | cyclone | pmtmr } |
|
|
|
clocksource= Override the default clocksource |
|
Format: <string> |
|
Override the default clocksource and use the clocksource |
|
with the name specified. |
|
Some clocksource names to choose from, depending on |
|
the platform: |
|
[all] jiffies (this is the base, fallback clocksource) |
|
[ACPI] acpi_pm |
|
[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, |
|
pxa_timer,timer3,32k_counter,timer0_1 |
|
[X86-32] pit,hpet,tsc; |
|
scx200_hrt on Geode; cyclone on IBM x440 |
|
[MIPS] MIPS |
|
[PARISC] cr16 |
|
[S390] tod |
|
[SH] SuperH |
|
[SPARC64] tick |
|
[X86-64] hpet,tsc |
|
|
|
clocksource.arm_arch_timer.evtstrm= |
|
[ARM,ARM64] |
|
Format: <bool> |
|
Enable/disable the eventstream feature of the ARM |
|
architected timer so that code using WFE-based polling |
|
loops can be debugged more effectively on production |
|
systems. |
|
|
|
clocksource.max_cswd_read_retries= [KNL] |
|
Number of clocksource_watchdog() retries due to |
|
external delays before the clock will be marked |
|
unstable. Defaults to three retries, that is, |
|
four attempts to read the clock under test. |
|
|
|
clocksource.verify_n_cpus= [KNL] |
|
Limit the number of CPUs checked for clocksources |
|
marked with CLOCK_SOURCE_VERIFY_PERCPU that |
|
are marked unstable due to excessive skew. |
|
A negative value says to check all CPUs, while |
|
zero says not to check any. Values larger than |
|
nr_cpu_ids are silently truncated to nr_cpu_ids. |
|
The actual CPUs are chosen randomly, with |
|
no replacement if the same CPU is chosen twice. |
|
|
|
clocksource-wdtest.holdoff= [KNL] |
|
Set the time in seconds that the clocksource |
|
watchdog test waits before commencing its tests. |
|
Defaults to zero when built as a module and to |
|
10 seconds when built into the kernel. |
|
|
|
clearcpuid=BITNUM[,BITNUM...] [X86] |
|
Disable CPUID feature X for the kernel. See |
|
arch/x86/include/asm/cpufeatures.h for the valid bit |
|
numbers. Note the Linux specific bits are not necessarily |
|
stable over kernel options, but the vendor specific |
|
ones should be. |
|
Also note that user programs calling CPUID directly |
|
or using the feature without checking anything |
|
will still see it. This just prevents it from |
|
being used by the kernel or shown in /proc/cpuinfo. |
|
Also note the kernel might malfunction if you disable |
|
some critical bits. |
|
|
|
cma=nn[MG]@[start[MG][-end[MG]]] |
|
[KNL,CMA] |
|
Sets the size of kernel global memory area for |
|
contiguous memory allocations and optionally the |
|
placement constraint by the physical address range of |
|
memory allocations. A value of 0 disables CMA |
|
altogether. For more information, see |
|
kernel/dma/contiguous.c |
|
|
|
cma_pernuma=nn[MG] |
|
[ARM64,KNL,CMA] |
|
Sets the size of kernel per-numa memory area for |
|
contiguous memory allocations. A value of 0 disables |
|
per-numa CMA altogether. And If this option is not |
|
specificed, the default value is 0. |
|
With per-numa CMA enabled, DMA users on node nid will |
|
first try to allocate buffer from the pernuma area |
|
which is located in node nid, if the allocation fails, |
|
they will fallback to the global default memory area. |
|
|
|
cmo_free_hint= [PPC] Format: { yes | no } |
|
Specify whether pages are marked as being inactive |
|
when they are freed. This is used in CMO environments |
|
to determine OS memory pressure for page stealing by |
|
a hypervisor. |
|
Default: yes |
|
|
|
coherent_pool=nn[KMG] [ARM,KNL] |
|
Sets the size of memory pool for coherent, atomic dma |
|
allocations, by default set to 256K. |
|
|
|
com20020= [HW,NET] ARCnet - COM20020 chipset |
|
Format: |
|
<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] |
|
|
|
com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) |
|
Format: <io>[,<irq>] |
|
|
|
com90xx= [HW,NET] |
|
ARCnet - COM90xx chipset (memory-mapped buffers) |
|
Format: <io>[,<irq>[,<memstart>]] |
|
|
|
condev= [HW,S390] console device |
|
conmode= |
|
|
|
console= [KNL] Output console device and options. |
|
|
|
tty<n> Use the virtual console device <n>. |
|
|
|
ttyS<n>[,options] |
|
ttyUSB0[,options] |
|
Use the specified serial port. The options are of |
|
the form "bbbbpnf", where "bbbb" is the baud rate, |
|
"p" is parity ("n", "o", or "e"), "n" is number of |
|
bits, and "f" is flow control ("r" for RTS or |
|
omit it). Default is "9600n8". |
|
|
|
See Documentation/admin-guide/serial-console.rst for more |
|
information. See |
|
Documentation/networking/netconsole.rst for an |
|
alternative. |
|
|
|
uart[8250],io,<addr>[,options] |
|
uart[8250],mmio,<addr>[,options] |
|
uart[8250],mmio16,<addr>[,options] |
|
uart[8250],mmio32,<addr>[,options] |
|
uart[8250],0x<addr>[,options] |
|
Start an early, polled-mode console on the 8250/16550 |
|
UART at the specified I/O port or MMIO address, |
|
switching to the matching ttyS device later. |
|
MMIO inter-register address stride is either 8-bit |
|
(mmio), 16-bit (mmio16), or 32-bit (mmio32). |
|
If none of [io|mmio|mmio16|mmio32], <addr> is assumed |
|
to be equivalent to 'mmio'. 'options' are specified in |
|
the same format described for ttyS above; if unspecified, |
|
the h/w is not re-initialized. |
|
|
|
hvc<n> Use the hypervisor console device <n>. This is for |
|
both Xen and PowerPC hypervisors. |
|
|
|
If the device connected to the port is not a TTY but a braille |
|
device, prepend "brl," before the device type, for instance |
|
console=brl,ttyS0 |
|
For now, only VisioBraille is supported. |
|
|
|
console_msg_format= |
|
[KNL] Change console messages format |
|
default |
|
By default we print messages on consoles in |
|
"[time stamp] text\n" format (time stamp may not be |
|
printed, depending on CONFIG_PRINTK_TIME or |
|
`printk_time' param). |
|
syslog |
|
Switch to syslog format: "<%u>[time stamp] text\n" |
|
IOW, each message will have a facility and loglevel |
|
prefix. The format is similar to one used by syslog() |
|
syscall, or to executing "dmesg -S --raw" or to reading |
|
from /proc/kmsg. |
|
|
|
consoleblank= [KNL] The console blank (screen saver) timeout in |
|
seconds. A value of 0 disables the blank timer. |
|
Defaults to 0. |
|
|
|
coredump_filter= |
|
[KNL] Change the default value for |
|
/proc/<pid>/coredump_filter. |
|
See also Documentation/filesystems/proc.rst. |
|
|
|
coresight_cpu_debug.enable |
|
[ARM,ARM64] |
|
Format: <bool> |
|
Enable/disable the CPU sampling based debugging. |
|
0: default value, disable debugging |
|
1: enable debugging at boot time |
|
|
|
cpuidle.off=1 [CPU_IDLE] |
|
disable the cpuidle sub-system |
|
|
|
cpuidle.governor= |
|
[CPU_IDLE] Name of the cpuidle governor to use. |
|
|
|
cpufreq.off=1 [CPU_FREQ] |
|
disable the cpufreq sub-system |
|
|
|
cpufreq.default_governor= |
|
[CPU_FREQ] Name of the default cpufreq governor or |
|
policy to use. This governor must be registered in the |
|
kernel before the cpufreq driver probes. |
|
|
|
cpu_init_udelay=N |
|
[X86] Delay for N microsec between assert and de-assert |
|
of APIC INIT to start processors. This delay occurs |
|
on every CPU online, such as boot, and resume from suspend. |
|
Default: 10000 |
|
|
|
cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver |
|
Format: |
|
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] |
|
|
|
crashkernel=size[KMG][@offset[KMG]] |
|
[KNL] Using kexec, Linux can switch to a 'crash kernel' |
|
upon panic. This parameter reserves the physical |
|
memory region [offset, offset + size] for that kernel |
|
image. If '@offset' is omitted, then a suitable offset |
|
is selected automatically. |
|
[KNL, X86-64] Select a region under 4G first, and |
|
fall back to reserve region above 4G when '@offset' |
|
hasn't been specified. |
|
See Documentation/admin-guide/kdump/kdump.rst for further details. |
|
|
|
crashkernel=range1:size1[,range2:size2,...][@offset] |
|
[KNL] Same as above, but depends on the memory |
|
in the running system. The syntax of range is |
|
start-[end] where start and end are both |
|
a memory unit (amount[KMG]). See also |
|
Documentation/admin-guide/kdump/kdump.rst for an example. |
|
|
|
crashkernel=size[KMG],high |
|
[KNL, X86-64] range could be above 4G. Allow kernel |
|
to allocate physical memory region from top, so could |
|
be above 4G if system have more than 4G ram installed. |
|
Otherwise memory region will be allocated below 4G, if |
|
available. |
|
It will be ignored if crashkernel=X is specified. |
|
crashkernel=size[KMG],low |
|
[KNL, X86-64] range under 4G. When crashkernel=X,high |
|
is passed, kernel could allocate physical memory region |
|
above 4G, that cause second kernel crash on system |
|
that require some amount of low memory, e.g. swiotlb |
|
requires at least 64M+32K low memory, also enough extra |
|
low memory is needed to make sure DMA buffers for 32-bit |
|
devices won't run out. Kernel would try to allocate at |
|
at least 256M below 4G automatically. |
|
This one let user to specify own low range under 4G |
|
for second kernel instead. |
|
0: to disable low allocation. |
|
It will be ignored when crashkernel=X,high is not used |
|
or memory reserved is below 4G. |
|
|
|
cryptomgr.notests |
|
[KNL] Disable crypto self-tests |
|
|
|
cs89x0_dma= [HW,NET] |
|
Format: <dma> |
|
|
|
cs89x0_media= [HW,NET] |
|
Format: { rj45 | aui | bnc } |
|
|
|
csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call |
|
handling. When switched on, additional debug data is |
|
printed to the console in case a hanging CPU is |
|
detected, and that CPU is pinged again in order to try |
|
to resolve the hang situation. |
|
0: disable csdlock debugging (default) |
|
1: enable basic csdlock debugging (minor impact) |
|
ext: enable extended csdlock debugging (more impact, |
|
but more data) |
|
|
|
dasd= [HW,NET] |
|
See header of drivers/s390/block/dasd_devmap.c. |
|
|
|
db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port |
|
(one device per port) |
|
Format: <port#>,<type> |
|
See also Documentation/input/devices/joystick-parport.rst |
|
|
|
ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot |
|
time. See |
|
Documentation/admin-guide/dynamic-debug-howto.rst for |
|
details. Deprecated, see dyndbg. |
|
|
|
debug [KNL] Enable kernel debugging (events log level). |
|
|
|
debug_boot_weak_hash |
|
[KNL] Enable printing [hashed] pointers early in the |
|
boot sequence. If enabled, we use a weak hash instead |
|
of siphash to hash pointers. Use this option if you are |
|
seeing instances of '(___ptrval___)') and need to see a |
|
value (hashed pointer) instead. Cryptographically |
|
insecure, please do not use on production kernels. |
|
|
|
debug_locks_verbose= |
|
[KNL] verbose locking self-tests |
|
Format: <int> |
|
Print debugging info while doing the locking API |
|
self-tests. |
|
Bitmask for the various LOCKTYPE_ tests. Defaults to 0 |
|
(no extra messages), setting it to -1 (all bits set) |
|
will print _a_lot_ more information - normally only |
|
useful to lockdep developers. |
|
|
|
debug_objects [KNL] Enable object debugging |
|
|
|
no_debug_objects |
|
[KNL] Disable object debugging |
|
|
|
debug_guardpage_minorder= |
|
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this |
|
parameter allows control of the order of pages that will |
|
be intentionally kept free (and hence protected) by the |
|
buddy allocator. Bigger value increase the probability |
|
of catching random memory corruption, but reduce the |
|
amount of memory for normal system use. The maximum |
|
possible value is MAX_ORDER/2. Setting this parameter |
|
to 1 or 2 should be enough to identify most random |
|
memory corruption problems caused by bugs in kernel or |
|
driver code when a CPU writes to (or reads from) a |
|
random memory location. Note that there exists a class |
|
of memory corruptions problems caused by buggy H/W or |
|
F/W or by drivers badly programing DMA (basically when |
|
memory is written at bus level and the CPU MMU is |
|
bypassed) which are not detectable by |
|
CONFIG_DEBUG_PAGEALLOC, hence this option will not help |
|
tracking down these problems. |
|
|
|
debug_pagealloc= |
|
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter |
|
enables the feature at boot time. By default, it is |
|
disabled and the system will work mostly the same as a |
|
kernel built without CONFIG_DEBUG_PAGEALLOC. |
|
Note: to get most of debug_pagealloc error reports, it's |
|
useful to also enable the page_owner functionality. |
|
on: enable the feature |
|
|
|
debugfs= [KNL] This parameter enables what is exposed to userspace |
|
and debugfs internal clients. |
|
Format: { on, no-mount, off } |
|
on: All functions are enabled. |
|
no-mount: |
|
Filesystem is not registered but kernel clients can |
|
access APIs and a crashkernel can be used to read |
|
its content. There is nothing to mount. |
|
off: Filesystem is not registered and clients |
|
get a -EPERM as result when trying to register files |
|
or directories within debugfs. |
|
This is equivalent of the runtime functionality if |
|
debugfs was not enabled in the kernel at all. |
|
Default value is set in build-time with a kernel configuration. |
|
|
|
debugpat [X86] Enable PAT debugging |
|
|
|
decnet.addr= [HW,NET] |
|
Format: <area>[,<node>] |
|
See also Documentation/networking/decnet.rst. |
|
|
|
default_hugepagesz= |
|
[HW] The size of the default HugeTLB page. This is |
|
the size represented by the legacy /proc/ hugepages |
|
APIs. In addition, this is the default hugetlb size |
|
used for shmget(), mmap() and mounting hugetlbfs |
|
filesystems. If not specified, defaults to the |
|
architecture's default huge page size. Huge page |
|
sizes are architecture dependent. See also |
|
Documentation/admin-guide/mm/hugetlbpage.rst. |
|
Format: size[KMG] |
|
|
|
deferred_probe_timeout= |
|
[KNL] Debugging option to set a timeout in seconds for |
|
deferred probe to give up waiting on dependencies to |
|
probe. Only specific dependencies (subsystems or |
|
drivers) that have opted in will be ignored. A timeout of 0 |
|
will timeout at the end of initcalls. This option will also |
|
dump out devices still on the deferred probe list after |
|
retrying. |
|
|
|
dfltcc= [HW,S390] |
|
Format: { on | off | def_only | inf_only | always } |
|
on: s390 zlib hardware support for compression on |
|
level 1 and decompression (default) |
|
off: No s390 zlib hardware support |
|
def_only: s390 zlib hardware support for deflate |
|
only (compression on level 1) |
|
inf_only: s390 zlib hardware support for inflate |
|
only (decompression) |
|
always: Same as 'on' but ignores the selected compression |
|
level always using hardware support (used for debugging) |
|
|
|
dhash_entries= [KNL] |
|
Set number of hash buckets for dentry cache. |
|
|
|
disable_1tb_segments [PPC] |
|
Disables the use of 1TB hash page table segments. This |
|
causes the kernel to fall back to 256MB segments which |
|
can be useful when debugging issues that require an SLB |
|
miss to occur. |
|
|
|
stress_slb [PPC] |
|
Limits the number of kernel SLB entries, and flushes |
|
them frequently to increase the rate of SLB faults |
|
on kernel addresses. |
|
|
|
disable= [IPV6] |
|
See Documentation/networking/ipv6.rst. |
|
|
|
hardened_usercopy= |
|
[KNL] Under CONFIG_HARDENED_USERCOPY, whether |
|
hardening is enabled for this boot. Hardened |
|
usercopy checking is used to protect the kernel |
|
from reading or writing beyond known memory |
|
allocation boundaries as a proactive defense |
|
against bounds-checking flaws in the kernel's |
|
copy_to_user()/copy_from_user() interface. |
|
on Perform hardened usercopy checks (default). |
|
off Disable hardened usercopy checks. |
|
|
|
disable_radix [PPC] |
|
Disable RADIX MMU mode on POWER9 |
|
|
|
radix_hcall_invalidate=on [PPC/PSERIES] |
|
Disable RADIX GTSE feature and use hcall for TLB |
|
invalidate. |
|
|
|
disable_tlbie [PPC] |
|
Disable TLBIE instruction. Currently does not work |
|
with KVM, with HASH MMU, or with coherent accelerators. |
|
|
|
disable_cpu_apicid= [X86,APIC,SMP] |
|
Format: <int> |
|
The number of initial APIC ID for the |
|
corresponding CPU to be disabled at boot, |
|
mostly used for the kdump 2nd kernel to |
|
disable BSP to wake up multiple CPUs without |
|
causing system reset or hang due to sending |
|
INIT from AP to BSP. |
|
|
|
disable_ddw [PPC/PSERIES] |
|
Disable Dynamic DMA Window support. Use this |
|
to workaround buggy firmware. |
|
|
|
disable_ipv6= [IPV6] |
|
See Documentation/networking/ipv6.rst. |
|
|
|
disable_mtrr_cleanup [X86] |
|
The kernel tries to adjust MTRR layout from continuous |
|
to discrete, to make X server driver able to add WB |
|
entry later. This parameter disables that. |
|
|
|
disable_mtrr_trim [X86, Intel and AMD only] |
|
By default the kernel will trim any uncacheable |
|
memory out of your available memory pool based on |
|
MTRR settings. This parameter disables that behavior, |
|
possibly causing your machine to run very slowly. |
|
|
|
disable_timer_pin_1 [X86] |
|
Disable PIN 1 of APIC timer |
|
Can be useful to work around chipset bugs. |
|
|
|
dis_ucode_ldr [X86] Disable the microcode loader. |
|
|
|
dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, |
|
this option disables the debugging code at boot. |
|
|
|
dma_debug_entries=<number> |
|
This option allows to tune the number of preallocated |
|
entries for DMA-API debugging code. One entry is |
|
required per DMA-API allocation. Use this if the |
|
DMA-API debugging code disables itself because the |
|
architectural default is too low. |
|
|
|
dma_debug_driver=<driver_name> |
|
With this option the DMA-API debugging driver |
|
filter feature can be enabled at boot time. Just |
|
pass the driver to filter for as the parameter. |
|
The filter can be disabled or changed to another |
|
driver later using sysfs. |
|
|
|
driver_async_probe= [KNL] |
|
List of driver names to be probed asynchronously. |
|
Format: <driver_name1>,<driver_name2>... |
|
|
|
drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] |
|
Broken monitors, graphic adapters, KVMs and EDIDless |
|
panels may send no or incorrect EDID data sets. |
|
This parameter allows to specify an EDID data sets |
|
in the /lib/firmware directory that are used instead. |
|
Generic built-in EDID data sets are used, if one of |
|
edid/1024x768.bin, edid/1280x1024.bin, |
|
edid/1680x1050.bin, or edid/1920x1080.bin is given |
|
and no file with the same name exists. Details and |
|
instructions how to build your own EDID data are |
|
available in Documentation/admin-guide/edid.rst. An EDID |
|
data set will only be used for a particular connector, |
|
if its name and a colon are prepended to the EDID |
|
name. Each connector may use a unique EDID data |
|
set by separating the files with a comma. An EDID |
|
data set with no connector name will be used for |
|
any connectors not explicitly specified. |
|
|
|
dscc4.setup= [NET] |
|
|
|
dt_cpu_ftrs= [PPC] |
|
Format: {"off" | "known"} |
|
Control how the dt_cpu_ftrs device-tree binding is |
|
used for CPU feature discovery and setup (if it |
|
exists). |
|
off: Do not use it, fall back to legacy cpu table. |
|
known: Do not pass through unknown features to guests |
|
or userspace, only those that the kernel is aware of. |
|
|
|
dump_apple_properties [X86] |
|
Dump name and content of EFI device properties on |
|
x86 Macs. Useful for driver authors to determine |
|
what data is available or for reverse-engineering. |
|
|
|
dyndbg[="val"] [KNL,DYNAMIC_DEBUG] |
|
<module>.dyndbg[="val"] |
|
Enable debug messages at boot time. See |
|
Documentation/admin-guide/dynamic-debug-howto.rst |
|
for details. |
|
|
|
nopku [X86] Disable Memory Protection Keys CPU feature found |
|
in some Intel CPUs. |
|
|
|
<module>.async_probe [KNL] |
|
Enable asynchronous probe on this module. |
|
|
|
early_ioremap_debug [KNL] |
|
Enable debug messages in early_ioremap support. This |
|
is useful for tracking down temporary early mappings |
|
which are not unmapped. |
|
|
|
earlycon= [KNL] Output early console device and options. |
|
|
|
When used with no options, the early console is |
|
determined by stdout-path property in device tree's |
|
chosen node or the ACPI SPCR table if supported by |
|
the platform. |
|
|
|
cdns,<addr>[,options] |
|
Start an early, polled-mode console on a Cadence |
|
(xuartps) serial port at the specified address. Only |
|
supported option is baud rate. If baud rate is not |
|
specified, the serial port must already be setup and |
|
configured. |
|
|
|
uart[8250],io,<addr>[,options] |
|
uart[8250],mmio,<addr>[,options] |
|
uart[8250],mmio32,<addr>[,options] |
|
uart[8250],mmio32be,<addr>[,options] |
|
uart[8250],0x<addr>[,options] |
|
Start an early, polled-mode console on the 8250/16550 |
|
UART at the specified I/O port or MMIO address. |
|
MMIO inter-register address stride is either 8-bit |
|
(mmio) or 32-bit (mmio32 or mmio32be). |
|
If none of [io|mmio|mmio32|mmio32be], <addr> is assumed |
|
to be equivalent to 'mmio'. 'options' are specified |
|
in the same format described for "console=ttyS<n>"; if |
|
unspecified, the h/w is not initialized. |
|
|
|
pl011,<addr> |
|
pl011,mmio32,<addr> |
|
Start an early, polled-mode console on a pl011 serial |
|
port at the specified address. The pl011 serial port |
|
must already be setup and configured. Options are not |
|
yet supported. If 'mmio32' is specified, then only |
|
the driver will use only 32-bit accessors to read/write |
|
the device registers. |
|
|
|
liteuart,<addr> |
|
Start an early console on a litex serial port at the |
|
specified address. The serial port must already be |
|
setup and configured. Options are not yet supported. |
|
|
|
meson,<addr> |
|
Start an early, polled-mode console on a meson serial |
|
port at the specified address. The serial port must |
|
already be setup and configured. Options are not yet |
|
supported. |
|
|
|
msm_serial,<addr> |
|
Start an early, polled-mode console on an msm serial |
|
port at the specified address. The serial port |
|
must already be setup and configured. Options are not |
|
yet supported. |
|
|
|
msm_serial_dm,<addr> |
|
Start an early, polled-mode console on an msm serial |
|
dm port at the specified address. The serial port |
|
must already be setup and configured. Options are not |
|
yet supported. |
|
|
|
owl,<addr> |
|
Start an early, polled-mode console on a serial port |
|
of an Actions Semi SoC, such as S500 or S900, at the |
|
specified address. The serial port must already be |
|
setup and configured. Options are not yet supported. |
|
|
|
rda,<addr> |
|
Start an early, polled-mode console on a serial port |
|
of an RDA Micro SoC, such as RDA8810PL, at the |
|
specified address. The serial port must already be |
|
setup and configured. Options are not yet supported. |
|
|
|
sbi |
|
Use RISC-V SBI (Supervisor Binary Interface) for early |
|
console. |
|
|
|
smh Use ARM semihosting calls for early console. |
|
|
|
s3c2410,<addr> |
|
s3c2412,<addr> |
|
s3c2440,<addr> |
|
s3c6400,<addr> |
|
s5pv210,<addr> |
|
exynos4210,<addr> |
|
Use early console provided by serial driver available |
|
on Samsung SoCs, requires selecting proper type and |
|
a correct base address of the selected UART port. The |
|
serial port must already be setup and configured. |
|
Options are not yet supported. |
|
|
|
lantiq,<addr> |
|
Start an early, polled-mode console on a lantiq serial |
|
(lqasc) port at the specified address. The serial port |
|
must already be setup and configured. Options are not |
|
yet supported. |
|
|
|
lpuart,<addr> |
|
lpuart32,<addr> |
|
Use early console provided by Freescale LP UART driver |
|
found on Freescale Vybrid and QorIQ LS1021A processors. |
|
A valid base address must be provided, and the serial |
|
port must already be setup and configured. |
|
|
|
ec_imx21,<addr> |
|
ec_imx6q,<addr> |
|
Start an early, polled-mode, output-only console on the |
|
Freescale i.MX UART at the specified address. The UART |
|
must already be setup and configured. |
|
|
|
ar3700_uart,<addr> |
|
Start an early, polled-mode console on the |
|
Armada 3700 serial port at the specified |
|
address. The serial port must already be setup |
|
and configured. Options are not yet supported. |
|
|
|
qcom_geni,<addr> |
|
Start an early, polled-mode console on a Qualcomm |
|
Generic Interface (GENI) based serial port at the |
|
specified address. The serial port must already be |
|
setup and configured. Options are not yet supported. |
|
|
|
efifb,[options] |
|
Start an early, unaccelerated console on the EFI |
|
memory mapped framebuffer (if available). On cache |
|
coherent non-x86 systems that use system memory for |
|
the framebuffer, pass the 'ram' option so that it is |
|
mapped with the correct attributes. |
|
|
|
linflex,<addr> |
|
Use early console provided by Freescale LINFlexD UART |
|
serial driver for NXP S32V234 SoCs. A valid base |
|
address must be provided, and the serial port must |
|
already be setup and configured. |
|
|
|
earlyprintk= [X86,SH,ARM,M68k,S390] |
|
earlyprintk=vga |
|
earlyprintk=sclp |
|
earlyprintk=xen |
|
earlyprintk=serial[,ttySn[,baudrate]] |
|
earlyprintk=serial[,0x...[,baudrate]] |
|
earlyprintk=ttySn[,baudrate] |
|
earlyprintk=dbgp[debugController#] |
|
earlyprintk=pciserial[,force],bus:device.function[,baudrate] |
|
earlyprintk=xdbc[xhciController#] |
|
|
|
earlyprintk is useful when the kernel crashes before |
|
the normal console is initialized. It is not enabled by |
|
default because it has some cosmetic problems. |
|
|
|
Append ",keep" to not disable it when the real console |
|
takes over. |
|
|
|
Only one of vga, efi, serial, or usb debug port can |
|
be used at a time. |
|
|
|
Currently only ttyS0 and ttyS1 may be specified by |
|
name. Other I/O ports may be explicitly specified |
|
on some architectures (x86 and arm at least) by |
|
replacing ttySn with an I/O port address, like this: |
|
earlyprintk=serial,0x1008,115200 |
|
You can find the port for a given device in |
|
/proc/tty/driver/serial: |
|
2: uart:ST16650V2 port:00001008 irq:18 ... |
|
|
|
Interaction with the standard serial driver is not |
|
very good. |
|
|
|
The VGA and EFI output is eventually overwritten by |
|
the real console. |
|
|
|
The xen option can only be used in Xen domains. |
|
|
|
The sclp output can only be used on s390. |
|
|
|
The optional "force" to "pciserial" enables use of a |
|
PCI device even when its classcode is not of the |
|
UART class. |
|
|
|
edac_report= [HW,EDAC] Control how to report EDAC event |
|
Format: {"on" | "off" | "force"} |
|
on: enable EDAC to report H/W event. May be overridden |
|
by other higher priority error reporting module. |
|
off: disable H/W event reporting through EDAC. |
|
force: enforce the use of EDAC to report H/W event. |
|
default: on. |
|
|
|
ekgdboc= [X86,KGDB] Allow early kernel console debugging |
|
ekgdboc=kbd |
|
|
|
This is designed to be used in conjunction with |
|
the boot argument: earlyprintk=vga |
|
|
|
This parameter works in place of the kgdboc parameter |
|
but can only be used if the backing tty is available |
|
very early in the boot process. For early debugging |
|
via a serial port see kgdboc_earlycon instead. |
|
|
|
edd= [EDD] |
|
Format: {"off" | "on" | "skip[mbr]"} |
|
|
|
efi= [EFI] |
|
Format: { "debug", "disable_early_pci_dma", |
|
"nochunk", "noruntime", "nosoftreserve", |
|
"novamap", "no_disable_early_pci_dma" } |
|
debug: enable misc debug output. |
|
disable_early_pci_dma: disable the busmaster bit on all |
|
PCI bridges while in the EFI boot stub. |
|
nochunk: disable reading files in "chunks" in the EFI |
|
boot stub, as chunking can cause problems with some |
|
firmware implementations. |
|
noruntime : disable EFI runtime services support |
|
nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) |
|
attribute may cause the kernel to reserve the |
|
memory range for a memory mapping driver to |
|
claim. Specify efi=nosoftreserve to disable this |
|
reservation and treat the memory by its base type |
|
(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). |
|
novamap: do not call SetVirtualAddressMap(). |
|
no_disable_early_pci_dma: Leave the busmaster bit set |
|
on all PCI bridges while in the EFI boot stub |
|
|
|
efi_no_storage_paranoia [EFI; X86] |
|
Using this parameter you can use more than 50% of |
|
your efi variable storage. Use this parameter only if |
|
you are really sure that your UEFI does sane gc and |
|
fulfills the spec otherwise your board may brick. |
|
|
|
efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] |
|
Add arbitrary attribute to specific memory range by |
|
updating original EFI memory map. |
|
Region of memory which aa attribute is added to is |
|
from ss to ss+nn. |
|
|
|
If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 |
|
is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) |
|
attribute is added to range 0x100000000-0x180000000 and |
|
0x10a0000000-0x1120000000. |
|
|
|
If efi_fake_mem=8G@9G:0x40000 is specified, the |
|
EFI_MEMORY_SP(0x40000) attribute is added to |
|
range 0x240000000-0x43fffffff. |
|
|
|
Using this parameter you can do debugging of EFI memmap |
|
related features. For example, you can do debugging of |
|
Address Range Mirroring feature even if your box |
|
doesn't support it, or mark specific memory as |
|
"soft reserved". |
|
|
|
efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT |
|
that is to be dynamically loaded by Linux. If there are |
|
multiple variables with the same name but with different |
|
vendor GUIDs, all of them will be loaded. See |
|
Documentation/admin-guide/acpi/ssdt-overlays.rst for details. |
|
|
|
|
|
eisa_irq_edge= [PARISC,HW] |
|
See header of drivers/parisc/eisa.c. |
|
|
|
elanfreq= [X86-32] |
|
See comment before function elanfreq_setup() in |
|
arch/x86/kernel/cpu/cpufreq/elanfreq.c. |
|
|
|
elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] |
|
Specifies physical address of start of kernel core |
|
image elf header and optionally the size. Generally |
|
kexec loader will pass this option to capture kernel. |
|
See Documentation/admin-guide/kdump/kdump.rst for details. |
|
|
|
enable_mtrr_cleanup [X86] |
|
The kernel tries to adjust MTRR layout from continuous |
|
to discrete, to make X server driver able to add WB |
|
entry later. This parameter enables that. |
|
|
|
enable_timer_pin_1 [X86] |
|
Enable PIN 1 of APIC timer |
|
Can be useful to work around chipset bugs |
|
(in particular on some ATI chipsets). |
|
The kernel tries to set a reasonable default. |
|
|
|
enforcing [SELINUX] Set initial enforcing status. |
|
Format: {"0" | "1"} |
|
See security/selinux/Kconfig help text. |
|
0 -- permissive (log only, no denials). |
|
1 -- enforcing (deny and log). |
|
Default value is 0. |
|
Value can be changed at runtime via |
|
/sys/fs/selinux/enforce. |
|
|
|
erst_disable [ACPI] |
|
Disable Error Record Serialization Table (ERST) |
|
support. |
|
|
|
ether= [HW,NET] Ethernet cards parameters |
|
This option is obsoleted by the "netdev=" option, which |
|
has equivalent usage. See its documentation for details. |
|
|
|
evm= [EVM] |
|
Format: { "fix" } |
|
Permit 'security.evm' to be updated regardless of |
|
current integrity status. |
|
|
|
failslab= |
|
fail_usercopy= |
|
fail_page_alloc= |
|
fail_make_request=[KNL] |
|
General fault injection mechanism. |
|
Format: <interval>,<probability>,<space>,<times> |
|
See also Documentation/fault-injection/. |
|
|
|
fb_tunnels= [NET] |
|
Format: { initns | none } |
|
See Documentation/admin-guide/sysctl/net.rst for |
|
fb_tunnels_only_for_init_ns |
|
|
|
floppy= [HW] |
|
See Documentation/admin-guide/blockdev/floppy.rst. |
|
|
|
force_pal_cache_flush |
|
[IA-64] Avoid check_sal_cache_flush which may hang on |
|
buggy SAL_CACHE_FLUSH implementations. Using this |
|
parameter will force ia64_sal_cache_flush to call |
|
ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. |
|
|
|
forcepae [X86-32] |
|
Forcefully enable Physical Address Extension (PAE). |
|
Many Pentium M systems disable PAE but may have a |
|
functionally usable PAE implementation. |
|
Warning: use of this parameter will taint the kernel |
|
and may cause unknown problems. |
|
|
|
ftrace=[tracer] |
|
[FTRACE] will set and start the specified tracer |
|
as early as possible in order to facilitate early |
|
boot debugging. |
|
|
|
ftrace_dump_on_oops[=orig_cpu] |
|
[FTRACE] will dump the trace buffers on oops. |
|
If no parameter is passed, ftrace will dump |
|
buffers of all CPUs, but if you pass orig_cpu, it will |
|
dump only the buffer of the CPU that triggered the |
|
oops. |
|
|
|
ftrace_filter=[function-list] |
|
[FTRACE] Limit the functions traced by the function |
|
tracer at boot up. function-list is a comma-separated |
|
list of functions. This list can be changed at run |
|
time by the set_ftrace_filter file in the debugfs |
|
tracing directory. |
|
|
|
ftrace_notrace=[function-list] |
|
[FTRACE] Do not trace the functions specified in |
|
function-list. This list can be changed at run time |
|
by the set_ftrace_notrace file in the debugfs |
|
tracing directory. |
|
|
|
ftrace_graph_filter=[function-list] |
|
[FTRACE] Limit the top level callers functions traced |
|
by the function graph tracer at boot up. |
|
function-list is a comma-separated list of functions |
|
that can be changed at run time by the |
|
set_graph_function file in the debugfs tracing directory. |
|
|
|
ftrace_graph_notrace=[function-list] |
|
[FTRACE] Do not trace from the functions specified in |
|
function-list. This list is a comma-separated list of |
|
functions that can be changed at run time by the |
|
set_graph_notrace file in the debugfs tracing directory. |
|
|
|
ftrace_graph_max_depth=<uint> |
|
[FTRACE] Used with the function graph tracer. This is |
|
the max depth it will trace into a function. This value |
|
can be changed at run time by the max_graph_depth file |
|
in the tracefs tracing directory. default: 0 (no limit) |
|
|
|
fw_devlink= [KNL] Create device links between consumer and supplier |
|
devices by scanning the firmware to infer the |
|
consumer/supplier relationships. This feature is |
|
especially useful when drivers are loaded as modules as |
|
it ensures proper ordering of tasks like device probing |
|
(suppliers first, then consumers), supplier boot state |
|
clean up (only after all consumers have probed), |
|
suspend/resume & runtime PM (consumers first, then |
|
suppliers). |
|
Format: { off | permissive | on | rpm } |
|
off -- Don't create device links from firmware info. |
|
permissive -- Create device links from firmware info |
|
but use it only for ordering boot state clean |
|
up (sync_state() calls). |
|
on -- Create device links from firmware info and use it |
|
to enforce probe and suspend/resume ordering. |
|
rpm -- Like "on", but also use to order runtime PM. |
|
|
|
fw_devlink.strict=<bool> |
|
[KNL] Treat all inferred dependencies as mandatory |
|
dependencies. This only applies for fw_devlink=on|rpm. |
|
Format: <bool> |
|
|
|
gamecon.map[2|3]= |
|
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad |
|
support via parallel port (up to 5 devices per port) |
|
Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> |
|
See also Documentation/input/devices/joystick-parport.rst |
|
|
|
gamma= [HW,DRM] |
|
|
|
gart_fix_e820= [X86-64] disable the fix e820 for K8 GART |
|
Format: off | on |
|
default: on |
|
|
|
gcov_persist= [GCOV] When non-zero (default), profiling data for |
|
kernel modules is saved and remains accessible via |
|
debugfs, even when the module is unloaded/reloaded. |
|
When zero, profiling data is discarded and associated |
|
debugfs files are removed at module unload time. |
|
|
|
goldfish [X86] Enable the goldfish android emulator platform. |
|
Don't use this when you are not running on the |
|
android emulator |
|
|
|
gpio-mockup.gpio_mockup_ranges |
|
[HW] Sets the ranges of gpiochip of for this device. |
|
Format: <start1>,<end1>,<start2>,<end2>... |
|
gpio-mockup.gpio_mockup_named_lines |
|
[HW] Let the driver know GPIO lines should be named. |
|
|
|
gpt [EFI] Forces disk with valid GPT signature but |
|
invalid Protective MBR to be treated as GPT. If the |
|
primary GPT is corrupted, it enables the backup/alternate |
|
GPT to be used instead. |
|
|
|
grcan.enable0= [HW] Configuration of physical interface 0. Determines |
|
the "Enable 0" bit of the configuration register. |
|
Format: 0 | 1 |
|
Default: 0 |
|
grcan.enable1= [HW] Configuration of physical interface 1. Determines |
|
the "Enable 0" bit of the configuration register. |
|
Format: 0 | 1 |
|
Default: 0 |
|
grcan.select= [HW] Select which physical interface to use. |
|
Format: 0 | 1 |
|
Default: 0 |
|
grcan.txsize= [HW] Sets the size of the tx buffer. |
|
Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. |
|
Default: 1024 |
|
grcan.rxsize= [HW] Sets the size of the rx buffer. |
|
Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. |
|
Default: 1024 |
|
|
|
hardlockup_all_cpu_backtrace= |
|
[KNL] Should the hard-lockup detector generate |
|
backtraces on all cpus. |
|
Format: 0 | 1 |
|
|
|
hashdist= [KNL,NUMA] Large hashes allocated during boot |
|
are distributed across NUMA nodes. Defaults on |
|
for 64-bit NUMA, off otherwise. |
|
Format: 0 | 1 (for off | on) |
|
|
|
hcl= [IA-64] SGI's Hardware Graph compatibility layer |
|
|
|
hd= [EIDE] (E)IDE hard drive subsystem geometry |
|
Format: <cyl>,<head>,<sect> |
|
|
|
hest_disable [ACPI] |
|
Disable Hardware Error Source Table (HEST) support; |
|
corresponding firmware-first mode error processing |
|
logic will be disabled. |
|
|
|
highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact |
|
size of <nn>. This works even on boxes that have no |
|
highmem otherwise. This also works to reduce highmem |
|
size on bigger boxes. |
|
|
|
highres= [KNL] Enable/disable high resolution timer mode. |
|
Valid parameters: "on", "off" |
|
Default: "on" |
|
|
|
hlt [BUGS=ARM,SH] |
|
|
|
hpet= [X86-32,HPET] option to control HPET usage |
|
Format: { enable (default) | disable | force | |
|
verbose } |
|
disable: disable HPET and use PIT instead |
|
force: allow force enabled of undocumented chips (ICH4, |
|
VIA, nVidia) |
|
verbose: show contents of HPET registers during setup |
|
|
|
hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET |
|
registers. Default set by CONFIG_HPET_MMAP_DEFAULT. |
|
|
|
hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation |
|
of gigantic hugepages. |
|
Format: nn[KMGTPE] |
|
|
|
Reserve a CMA area of given size and allocate gigantic |
|
hugepages using the CMA allocator. If enabled, the |
|
boot-time allocation of gigantic hugepages is skipped. |
|
|
|
hugepages= [HW] Number of HugeTLB pages to allocate at boot. |
|
If this follows hugepagesz (below), it specifies |
|
the number of pages of hugepagesz to be allocated. |
|
If this is the first HugeTLB parameter on the command |
|
line, it specifies the number of pages to allocate for |
|
the default huge page size. See also |
|
Documentation/admin-guide/mm/hugetlbpage.rst. |
|
Format: <integer> |
|
|
|
hugepagesz= |
|
[HW] The size of the HugeTLB pages. This is used in |
|
conjunction with hugepages (above) to allocate huge |
|
pages of a specific size at boot. The pair |
|
hugepagesz=X hugepages=Y can be specified once for |
|
each supported huge page size. Huge page sizes are |
|
architecture dependent. See also |
|
Documentation/admin-guide/mm/hugetlbpage.rst. |
|
Format: size[KMG] |
|
|
|
hugetlb_free_vmemmap= |
|
[KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP |
|
enabled. |
|
Allows heavy hugetlb users to free up some more |
|
memory (6 * PAGE_SIZE for each 2MB hugetlb page). |
|
Format: { on | off (default) } |
|
|
|
on: enable the feature |
|
off: disable the feature |
|
|
|
Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y, |
|
the default is on. |
|
|
|
This is not compatible with memory_hotplug.memmap_on_memory. |
|
If both parameters are enabled, hugetlb_free_vmemmap takes |
|
precedence over memory_hotplug.memmap_on_memory. |
|
|
|
hung_task_panic= |
|
[KNL] Should the hung task detector generate panics. |
|
Format: 0 | 1 |
|
|
|
A value of 1 instructs the kernel to panic when a |
|
hung task is detected. The default value is controlled |
|
by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time |
|
option. The value selected by this boot parameter can |
|
be changed later by the kernel.hung_task_panic sysctl. |
|
|
|
hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) |
|
terminal devices. Valid values: 0..8 |
|
hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. |
|
If specified, z/VM IUCV HVC accepts connections |
|
from listed z/VM user IDs only. |
|
|
|
hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations |
|
which allow the hypervisor to 'idle' the |
|
guest on lock contention. |
|
|
|
keep_bootcon [KNL] |
|
Do not unregister boot console at start. This is only |
|
useful for debugging when something happens in the window |
|
between unregistering the boot console and initializing |
|
the real console. |
|
|
|
i2c_bus= [HW] Override the default board specific I2C bus speed |
|
or register an additional I2C bus that is not |
|
registered from board initialization code. |
|
Format: |
|
<bus_id>,<clkrate> |
|
|
|
i8042.debug [HW] Toggle i8042 debug mode |
|
i8042.unmask_kbd_data |
|
[HW] Enable printing of interrupt data from the KBD port |
|
(disabled by default, and as a pre-condition |
|
requires that i8042.debug=1 be enabled) |
|
i8042.direct [HW] Put keyboard port into non-translated mode |
|
i8042.dumbkbd [HW] Pretend that controller can only read data from |
|
keyboard and cannot control its state |
|
(Don't attempt to blink the leds) |
|
i8042.noaux [HW] Don't check for auxiliary (== mouse) port |
|
i8042.nokbd [HW] Don't check/create keyboard port |
|
i8042.noloop [HW] Disable the AUX Loopback command while probing |
|
for the AUX port |
|
i8042.nomux [HW] Don't check presence of an active multiplexing |
|
controller |
|
i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX |
|
controllers |
|
i8042.notimeout [HW] Ignore timeout condition signalled by controller |
|
i8042.reset [HW] Reset the controller during init, cleanup and |
|
suspend-to-ram transitions, only during s2r |
|
transitions, or never reset |
|
Format: { 1 | Y | y | 0 | N | n } |
|
1, Y, y: always reset controller |
|
0, N, n: don't ever reset controller |
|
Default: only on s2r transitions on x86; most other |
|
architectures force reset to be always executed |
|
i8042.unlock [HW] Unlock (ignore) the keylock |
|
i8042.kbdreset [HW] Reset device connected to KBD port |
|
|
|
i810= [HW,DRM] |
|
|
|
i8k.ignore_dmi [HW] Continue probing hardware even if DMI data |
|
indicates that the driver is running on unsupported |
|
hardware. |
|
i8k.force [HW] Activate i8k driver even if SMM BIOS signature |
|
does not match list of supported models. |
|
i8k.power_status |
|
[HW] Report power status in /proc/i8k |
|
(disabled by default) |
|
i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN |
|
capability is set. |
|
|
|
i915.invert_brightness= |
|
[DRM] Invert the sense of the variable that is used to |
|
set the brightness of the panel backlight. Normally a |
|
brightness value of 0 indicates backlight switched off, |
|
and the maximum of the brightness value sets the backlight |
|
to maximum brightness. If this parameter is set to 0 |
|
(default) and the machine requires it, or this parameter |
|
is set to 1, a brightness value of 0 sets the backlight |
|
to maximum brightness, and the maximum of the brightness |
|
value switches the backlight off. |
|
-1 -- never invert brightness |
|
0 -- machine default |
|
1 -- force brightness inversion |
|
|
|
icn= [HW,ISDN] |
|
Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] |
|
|
|
ide-core.nodma= [HW] (E)IDE subsystem |
|
Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc |
|
.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr |
|
.cdrom .chs .ignore_cable are additional options |
|
See Documentation/ide/ide.rst. |
|
|
|
ide-generic.probe-mask= [HW] (E)IDE subsystem |
|
Format: <int> |
|
Probe mask for legacy ISA IDE ports. Depending on |
|
platform up to 6 ports are supported, enabled by |
|
setting corresponding bits in the mask to 1. The |
|
default value is 0x0, which has a special meaning. |
|
On systems that have PCI, it triggers scanning the |
|
PCI bus for the first and the second port, which |
|
are then probed. On systems without PCI the value |
|
of 0x0 enables probing the two first ports as if it |
|
was 0x3. |
|
|
|
ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem |
|
Claim all unknown PCI IDE storage controllers. |
|
|
|
idle= [X86] |
|
Format: idle=poll, idle=halt, idle=nomwait |
|
Poll forces a polling idle loop that can slightly |
|
improve the performance of waking up a idle CPU, but |
|
will use a lot of power and make the system run hot. |
|
Not recommended. |
|
idle=halt: Halt is forced to be used for CPU idle. |
|
In such case C2/C3 won't be used again. |
|
idle=nomwait: Disable mwait for CPU C-states |
|
|
|
idxd.sva= [HW] |
|
Format: <bool> |
|
Allow force disabling of Shared Virtual Memory (SVA) |
|
support for the idxd driver. By default it is set to |
|
true (1). |
|
|
|
idxd.tc_override= [HW] |
|
Format: <bool> |
|
Allow override of default traffic class configuration |
|
for the device. By default it is set to false (0). |
|
|
|
ieee754= [MIPS] Select IEEE Std 754 conformance mode |
|
Format: { strict | legacy | 2008 | relaxed } |
|
Default: strict |
|
|
|
Choose which programs will be accepted for execution |
|
based on the IEEE 754 NaN encoding(s) supported by |
|
the FPU and the NaN encoding requested with the value |
|
of an ELF file header flag individually set by each |
|
binary. Hardware implementations are permitted to |
|
support either or both of the legacy and the 2008 NaN |
|
encoding mode. |
|
|
|
Available settings are as follows: |
|
strict accept binaries that request a NaN encoding |
|
supported by the FPU |
|
legacy only accept legacy-NaN binaries, if supported |
|
by the FPU |
|
2008 only accept 2008-NaN binaries, if supported |
|
by the FPU |
|
relaxed accept any binaries regardless of whether |
|
supported by the FPU |
|
|
|
The FPU emulator is always able to support both NaN |
|
encodings, so if no FPU hardware is present or it has |
|
been disabled with 'nofpu', then the settings of |
|
'legacy' and '2008' strap the emulator accordingly, |
|
'relaxed' straps the emulator for both legacy-NaN and |
|
2008-NaN, whereas 'strict' enables legacy-NaN only on |
|
legacy processors and both NaN encodings on MIPS32 or |
|
MIPS64 CPUs. |
|
|
|
The setting for ABS.fmt/NEG.fmt instruction execution |
|
mode generally follows that for the NaN encoding, |
|
except where unsupported by hardware. |
|
|
|
ignore_loglevel [KNL] |
|
Ignore loglevel setting - this will print /all/ |
|
kernel messages to the console. Useful for debugging. |
|
We also add it as printk module parameter, so users |
|
could change it dynamically, usually by |
|
/sys/module/printk/parameters/ignore_loglevel. |
|
|
|
ignore_rlimit_data |
|
Ignore RLIMIT_DATA setting for data mappings, |
|
print warning at first misuse. Can be changed via |
|
/sys/module/kernel/parameters/ignore_rlimit_data. |
|
|
|
ihash_entries= [KNL] |
|
Set number of hash buckets for inode cache. |
|
|
|
ima_appraise= [IMA] appraise integrity measurements |
|
Format: { "off" | "enforce" | "fix" | "log" } |
|
default: "enforce" |
|
|
|
ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. |
|
The builtin appraise policy appraises all files |
|
owned by uid=0. |
|
|
|
ima_canonical_fmt [IMA] |
|
Use the canonical format for the binary runtime |
|
measurements, instead of host native format. |
|
|
|
ima_hash= [IMA] |
|
Format: { md5 | sha1 | rmd160 | sha256 | sha384 |
|
| sha512 | ... } |
|
default: "sha1" |
|
|
|
The list of supported hash algorithms is defined |
|
in crypto/hash_info.h. |
|
|
|
ima_policy= [IMA] |
|
The builtin policies to load during IMA setup. |
|
Format: "tcb | appraise_tcb | secure_boot | |
|
fail_securely | critical_data" |
|
|
|
The "tcb" policy measures all programs exec'd, files |
|
mmap'd for exec, and all files opened with the read |
|
mode bit set by either the effective uid (euid=0) or |
|
uid=0. |
|
|
|
The "appraise_tcb" policy appraises the integrity of |
|
all files owned by root. |
|
|
|
The "secure_boot" policy appraises the integrity |
|
of files (eg. kexec kernel image, kernel modules, |
|
firmware, policy, etc) based on file signatures. |
|
|
|
The "fail_securely" policy forces file signature |
|
verification failure also on privileged mounted |
|
filesystems with the SB_I_UNVERIFIABLE_SIGNATURE |
|
flag. |
|
|
|
The "critical_data" policy measures kernel integrity |
|
critical data. |
|
|
|
ima_tcb [IMA] Deprecated. Use ima_policy= instead. |
|
Load a policy which meets the needs of the Trusted |
|
Computing Base. This means IMA will measure all |
|
programs exec'd, files mmap'd for exec, and all files |
|
opened for read by uid=0. |
|
|
|
ima_template= [IMA] |
|
Select one of defined IMA measurements template formats. |
|
Formats: { "ima" | "ima-ng" | "ima-sig" } |
|
Default: "ima-ng" |
|
|
|
ima_template_fmt= |
|
[IMA] Define a custom template format. |
|
Format: { "field1|...|fieldN" } |
|
|
|
ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage |
|
Format: <min_file_size> |
|
Set the minimal file size for using asynchronous hash. |
|
If left unspecified, ahash usage is disabled. |
|
|
|
ahash performance varies for different data sizes on |
|
different crypto accelerators. This option can be used |
|
to achieve the best performance for a particular HW. |
|
|
|
ima.ahash_bufsize= [IMA] Asynchronous hash buffer size |
|
Format: <bufsize> |
|
Set hashing buffer size. Default: 4k. |
|
|
|
ahash performance varies for different chunk sizes on |
|
different crypto accelerators. This option can be used |
|
to achieve best performance for particular HW. |
|
|
|
init= [KNL] |
|
Format: <full_path> |
|
Run specified binary instead of /sbin/init as init |
|
process. |
|
|
|
initcall_debug [KNL] Trace initcalls as they are executed. Useful |
|
for working out where the kernel is dying during |
|
startup. |
|
|
|
initcall_blacklist= [KNL] Do not execute a comma-separated list of |
|
initcall functions. Useful for debugging built-in |
|
modules and initcalls. |
|
|
|
initramfs_async= [KNL] |
|
Format: <bool> |
|
Default: 1 |
|
This parameter controls whether the initramfs |
|
image is unpacked asynchronously, concurrently |
|
with devices being probed and |
|
initialized. This should normally just work, |
|
but as a debugging aid, one can get the |
|
historical behaviour of the initramfs |
|
unpacking being completed before device_ and |
|
late_ initcalls. |
|
|
|
initrd= [BOOT] Specify the location of the initial ramdisk |
|
|
|
initrdmem= [KNL] Specify a physical address and size from which to |
|
load the initrd. If an initrd is compiled in or |
|
specified in the bootparams, it takes priority over this |
|
setting. |
|
Format: ss[KMG],nn[KMG] |
|
Default is 0, 0 |
|
|
|
init_on_alloc= [MM] Fill newly allocated pages and heap objects with |
|
zeroes. |
|
Format: 0 | 1 |
|
Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. |
|
|
|
init_on_free= [MM] Fill freed pages and heap objects with zeroes. |
|
Format: 0 | 1 |
|
Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. |
|
|
|
init_pkru= [X86] Specify the default memory protection keys rights |
|
register contents for all processes. 0x55555554 by |
|
default (disallow access to all but pkey 0). Can |
|
override in debugfs after boot. |
|
|
|
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver |
|
Format: <irq> |
|
|
|
int_pln_enable [X86] Enable power limit notification interrupt |
|
|
|
integrity_audit=[IMA] |
|
Format: { "0" | "1" } |
|
0 -- basic integrity auditing messages. (Default) |
|
1 -- additional integrity auditing messages. |
|
|
|
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option |
|
on |
|
Enable intel iommu driver. |
|
off |
|
Disable intel iommu driver. |
|
igfx_off [Default Off] |
|
By default, gfx is mapped as normal device. If a gfx |
|
device has a dedicated DMAR unit, the DMAR unit is |
|
bypassed by not enabling DMAR with this option. In |
|
this case, gfx device will use physical address for |
|
DMA. |
|
strict [Default Off] |
|
Deprecated, equivalent to iommu.strict=1. |
|
sp_off [Default Off] |
|
By default, super page will be supported if Intel IOMMU |
|
has the capability. With this option, super page will |
|
not be supported. |
|
sm_on |
|
Enable the Intel IOMMU scalable mode if the hardware |
|
advertises that it has support for the scalable mode |
|
translation. |
|
sm_off |
|
Disallow use of the Intel IOMMU scalable mode. |
|
tboot_noforce [Default Off] |
|
Do not force the Intel IOMMU enabled under tboot. |
|
By default, tboot will force Intel IOMMU on, which |
|
could harm performance of some high-throughput |
|
devices like 40GBit network cards, even if identity |
|
mapping is enabled. |
|
Note that using this option lowers the security |
|
provided by tboot because it makes the system |
|
vulnerable to DMA attacks. |
|
|
|
intel_idle.max_cstate= [KNL,HW,ACPI,X86] |
|
0 disables intel_idle and fall back on acpi_idle. |
|
1 to 9 specify maximum depth of C-state. |
|
|
|
intel_pstate= [X86] |
|
disable |
|
Do not enable intel_pstate as the default |
|
scaling driver for the supported processors |
|
passive |
|
Use intel_pstate as a scaling driver, but configure it |
|
to work with generic cpufreq governors (instead of |
|
enabling its internal governor). This mode cannot be |
|
used along with the hardware-managed P-states (HWP) |
|
feature. |
|
force |
|
Enable intel_pstate on systems that prohibit it by default |
|
in favor of acpi-cpufreq. Forcing the intel_pstate driver |
|
instead of acpi-cpufreq may disable platform features, such |
|
as thermal controls and power capping, that rely on ACPI |
|
P-States information being indicated to OSPM and therefore |
|
should be used with caution. This option does not work with |
|
processors that aren't supported by the intel_pstate driver |
|
or on platforms that use pcc-cpufreq instead of acpi-cpufreq. |
|
no_hwp |
|
Do not enable hardware P state control (HWP) |
|
if available. |
|
hwp_only |
|
Only load intel_pstate on systems which support |
|
hardware P state control (HWP) if available. |
|
support_acpi_ppc |
|
Enforce ACPI _PPC performance limits. If the Fixed ACPI |
|
Description Table, specifies preferred power management |
|
profile as "Enterprise Server" or "Performance Server", |
|
then this feature is turned on by default. |
|
per_cpu_perf_limits |
|
Allow per-logical-CPU P-State performance control limits using |
|
cpufreq sysfs interface |
|
|
|
intremap= [X86-64, Intel-IOMMU] |
|
on enable Interrupt Remapping (default) |
|
off disable Interrupt Remapping |
|
nosid disable Source ID checking |
|
no_x2apic_optout |
|
BIOS x2APIC opt-out request will be ignored |
|
nopost disable Interrupt Posting |
|
|
|
iomem= Disable strict checking of access to MMIO memory |
|
strict regions from userspace. |
|
relaxed |
|
|
|
iommu= [X86] |
|
off |
|
force |
|
noforce |
|
biomerge |
|
panic |
|
nopanic |
|
merge |
|
nomerge |
|
soft |
|
pt [X86] |
|
nopt [X86] |
|
nobypass [PPC/POWERNV] |
|
Disable IOMMU bypass, using IOMMU for PCI devices. |
|
|
|
iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. |
|
Format: { "0" | "1" } |
|
0 - Try to allocate a 32-bit DMA address first, before |
|
falling back to the full range if needed. |
|
1 - Allocate directly from the full usable range, |
|
forcing Dual Address Cycle for PCI cards supporting |
|
greater than 32-bit addressing. |
|
|
|
iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour |
|
Format: { "0" | "1" } |
|
0 - Lazy mode. |
|
Request that DMA unmap operations use deferred |
|
invalidation of hardware TLBs, for increased |
|
throughput at the cost of reduced device isolation. |
|
Will fall back to strict mode if not supported by |
|
the relevant IOMMU driver. |
|
1 - Strict mode. |
|
DMA unmap operations invalidate IOMMU hardware TLBs |
|
synchronously. |
|
unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. |
|
Note: on x86, strict mode specified via one of the |
|
legacy driver-specific options takes precedence. |
|
|
|
iommu.passthrough= |
|
[ARM64, X86] Configure DMA to bypass the IOMMU by default. |
|
Format: { "0" | "1" } |
|
0 - Use IOMMU translation for DMA. |
|
1 - Bypass the IOMMU for DMA. |
|
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. |
|
|
|
io7= [HW] IO7 for Marvel-based Alpha systems |
|
See comment before marvel_specify_io7 in |
|
arch/alpha/kernel/core_marvel.c. |
|
|
|
io_delay= [X86] I/O delay method |
|
0x80 |
|
Standard port 0x80 based delay |
|
0xed |
|
Alternate port 0xed based delay (needed on some systems) |
|
udelay |
|
Simple two microseconds delay |
|
none |
|
No delay |
|
|
|
ip= [IP_PNP] |
|
See Documentation/admin-guide/nfs/nfsroot.rst. |
|
|
|
ipcmni_extend [KNL] Extend the maximum number of unique System V |
|
IPC identifiers from 32,768 to 16,777,216. |
|
|
|
irqaffinity= [SMP] Set the default irq affinity mask |
|
The argument is a cpu list, as described above. |
|
|
|
irqchip.gicv2_force_probe= |
|
[ARM, ARM64] |
|
Format: <bool> |
|
Force the kernel to look for the second 4kB page |
|
of a GICv2 controller even if the memory range |
|
exposed by the device tree is too small. |
|
|
|
irqchip.gicv3_nolpi= |
|
[ARM, ARM64] |
|
Force the kernel to ignore the availability of |
|
LPIs (and by consequence ITSs). Intended for system |
|
that use the kernel as a bootloader, and thus want |
|
to let secondary kernels in charge of setting up |
|
LPIs. |
|
|
|
irqchip.gicv3_pseudo_nmi= [ARM64] |
|
Enables support for pseudo-NMIs in the kernel. This |
|
requires the kernel to be built with |
|
CONFIG_ARM64_PSEUDO_NMI. |
|
|
|
irqfixup [HW] |
|
When an interrupt is not handled search all handlers |
|
for it. Intended to get systems with badly broken |
|
firmware running. |
|
|
|
irqpoll [HW] |
|
When an interrupt is not handled search all handlers |
|
for it. Also check all handlers each timer |
|
interrupt. Intended to get systems with badly broken |
|
firmware running. |
|
|
|
isapnp= [ISAPNP] |
|
Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
|
|
|
isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. |
|
[Deprecated - use cpusets instead] |
|
Format: [flag-list,]<cpu-list> |
|
|
|
Specify one or more CPUs to isolate from disturbances |
|
specified in the flag list (default: domain): |
|
|
|
nohz |
|
Disable the tick when a single task runs. |
|
|
|
A residual 1Hz tick is offloaded to workqueues, which you |
|
need to affine to housekeeping through the global |
|
workqueue's affinity configured via the |
|
/sys/devices/virtual/workqueue/cpumask sysfs file, or |
|
by using the 'domain' flag described below. |
|
|
|
NOTE: by default the global workqueue runs on all CPUs, |
|
so to protect individual CPUs the 'cpumask' file has to |
|
be configured manually after bootup. |
|
|
|
domain |
|
Isolate from the general SMP balancing and scheduling |
|
algorithms. Note that performing domain isolation this way |
|
is irreversible: it's not possible to bring back a CPU to |
|
the domains once isolated through isolcpus. It's strongly |
|
advised to use cpusets instead to disable scheduler load |
|
balancing through the "cpuset.sched_load_balance" file. |
|
It offers a much more flexible interface where CPUs can |
|
move in and out of an isolated set anytime. |
|
|
|
You can move a process onto or off an "isolated" CPU via |
|
the CPU affinity syscalls or cpuset. |
|
<cpu number> begins at 0 and the maximum value is |
|
"number of CPUs in system - 1". |
|
|
|
managed_irq |
|
|
|
Isolate from being targeted by managed interrupts |
|
which have an interrupt mask containing isolated |
|
CPUs. The affinity of managed interrupts is |
|
handled by the kernel and cannot be changed via |
|
the /proc/irq/* interfaces. |
|
|
|
This isolation is best effort and only effective |
|
if the automatically assigned interrupt mask of a |
|
device queue contains isolated and housekeeping |
|
CPUs. If housekeeping CPUs are online then such |
|
interrupts are directed to the housekeeping CPU |
|
so that IO submitted on the housekeeping CPU |
|
cannot disturb the isolated CPU. |
|
|
|
If a queue's affinity mask contains only isolated |
|
CPUs then this parameter has no effect on the |
|
interrupt routing decision, though interrupts are |
|
only delivered when tasks running on those |
|
isolated CPUs submit IO. IO submitted on |
|
housekeeping CPUs has no influence on those |
|
queues. |
|
|
|
The format of <cpu-list> is described above. |
|
|
|
iucv= [HW,NET] |
|
|
|
ivrs_ioapic [HW,X86-64] |
|
Provide an override to the IOAPIC-ID<->DEVICE-ID |
|
mapping provided in the IVRS ACPI table. For |
|
example, to map IOAPIC-ID decimal 10 to |
|
PCI device 00:14.0 write the parameter as: |
|
ivrs_ioapic[10]=00:14.0 |
|
|
|
ivrs_hpet [HW,X86-64] |
|
Provide an override to the HPET-ID<->DEVICE-ID |
|
mapping provided in the IVRS ACPI table. For |
|
example, to map HPET-ID decimal 0 to |
|
PCI device 00:14.0 write the parameter as: |
|
ivrs_hpet[0]=00:14.0 |
|
|
|
ivrs_acpihid [HW,X86-64] |
|
Provide an override to the ACPI-HID:UID<->DEVICE-ID |
|
mapping provided in the IVRS ACPI table. For |
|
example, to map UART-HID:UID AMD0020:0 to |
|
PCI device 00:14.5 write the parameter as: |
|
ivrs_acpihid[00:14.5]=AMD0020:0 |
|
|
|
js= [HW,JOY] Analog joystick |
|
See Documentation/input/joydev/joystick.rst. |
|
|
|
nokaslr [KNL] |
|
When CONFIG_RANDOMIZE_BASE is set, this disables |
|
kernel and module base offset ASLR (Address Space |
|
Layout Randomization). |
|
|
|
kasan_multi_shot |
|
[KNL] Enforce KASAN (Kernel Address Sanitizer) to print |
|
report on every invalid memory access. Without this |
|
parameter KASAN will print report only for the first |
|
invalid access. |
|
|
|
keepinitrd [HW,ARM] |
|
|
|
kernelcore= [KNL,X86,IA-64,PPC] |
|
Format: nn[KMGTPE] | nn% | "mirror" |
|
This parameter specifies the amount of memory usable by |
|
the kernel for non-movable allocations. The requested |
|
amount is spread evenly throughout all nodes in the |
|
system as ZONE_NORMAL. The remaining memory is used for |
|
movable memory in its own zone, ZONE_MOVABLE. In the |
|
event, a node is too small to have both ZONE_NORMAL and |
|
ZONE_MOVABLE, kernelcore memory will take priority and |
|
other nodes will have a larger ZONE_MOVABLE. |
|
|
|
ZONE_MOVABLE is used for the allocation of pages that |
|
may be reclaimed or moved by the page migration |
|
subsystem. Note that allocations like PTEs-from-HighMem |
|
still use the HighMem zone if it exists, and the Normal |
|
zone if it does not. |
|
|
|
It is possible to specify the exact amount of memory in |
|
the form of "nn[KMGTPE]", a percentage of total system |
|
memory in the form of "nn%", or "mirror". If "mirror" |
|
option is specified, mirrored (reliable) memory is used |
|
for non-movable allocations and remaining memory is used |
|
for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" |
|
are exclusive, so you cannot specify multiple forms. |
|
|
|
kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. |
|
Format: <Controller#>[,poll interval] |
|
The controller # is the number of the ehci usb debug |
|
port as it is probed via PCI. The poll interval is |
|
optional and is the number seconds in between |
|
each poll cycle to the debug port in case you need |
|
the functionality for interrupting the kernel with |
|
gdb or control-c on the dbgp connection. When |
|
not using this parameter you use sysrq-g to break into |
|
the kernel debugger. |
|
|
|
kgdboc= [KGDB,HW] kgdb over consoles. |
|
Requires a tty driver that supports console polling, |
|
or a supported polling keyboard driver (non-usb). |
|
Serial only format: <serial_device>[,baud] |
|
keyboard only format: kbd |
|
keyboard and serial format: kbd,<serial_device>[,baud] |
|
Optional Kernel mode setting: |
|
kms, kbd format: kms,kbd |
|
kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] |
|
|
|
kgdboc_earlycon= [KGDB,HW] |
|
If the boot console provides the ability to read |
|
characters and can work in polling mode, you can use |
|
this parameter to tell kgdb to use it as a backend |
|
until the normal console is registered. Intended to |
|
be used together with the kgdboc parameter which |
|
specifies the normal console to transition to. |
|
|
|
The name of the early console should be specified |
|
as the value of this parameter. Note that the name of |
|
the early console might be different than the tty |
|
name passed to kgdboc. It's OK to leave the value |
|
blank and the first boot console that implements |
|
read() will be picked. |
|
|
|
kgdbwait [KGDB] Stop kernel execution and enter the |
|
kernel debugger at the earliest opportunity. |
|
|
|
kmac= [MIPS] Korina ethernet MAC address. |
|
Configure the RouterBoard 532 series on-chip |
|
Ethernet adapter MAC address. |
|
|
|
kmemleak= [KNL] Boot-time kmemleak enable/disable |
|
Valid arguments: on, off |
|
Default: on |
|
Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, |
|
the default is off. |
|
|
|
kprobe_event=[probe-list] |
|
[FTRACE] Add kprobe events and enable at boot time. |
|
The probe-list is a semicolon delimited list of probe |
|
definitions. Each definition is same as kprobe_events |
|
interface, but the parameters are comma delimited. |
|
For example, to add a kprobe event on vfs_read with |
|
arg1 and arg2, add to the command line; |
|
|
|
kprobe_event=p,vfs_read,$arg1,$arg2 |
|
|
|
See also Documentation/trace/kprobetrace.rst "Kernel |
|
Boot Parameter" section. |
|
|
|
kpti= [ARM64] Control page table isolation of user |
|
and kernel address spaces. |
|
Default: enabled on cores which need mitigation. |
|
0: force disabled |
|
1: force enabled |
|
|
|
kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. |
|
Default is 0 (don't ignore, but inject #GP) |
|
|
|
kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. |
|
Default is false (don't support). |
|
|
|
kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit |
|
KVM MMU at runtime. |
|
Default is 0 (off) |
|
|
|
kvm.nx_huge_pages= |
|
[KVM] Controls the software workaround for the |
|
X86_BUG_ITLB_MULTIHIT bug. |
|
force : Always deploy workaround. |
|
off : Never deploy workaround. |
|
auto : Deploy workaround based on the presence of |
|
X86_BUG_ITLB_MULTIHIT. |
|
|
|
Default is 'auto'. |
|
|
|
If the software workaround is enabled for the host, |
|
guests do need not to enable it for nested guests. |
|
|
|
kvm.nx_huge_pages_recovery_ratio= |
|
[KVM] Controls how many 4KiB pages are periodically zapped |
|
back to huge pages. 0 disables the recovery, otherwise if |
|
the value is N KVM will zap 1/Nth of the 4KiB pages every |
|
minute. The default is 60. |
|
|
|
kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. |
|
Default is 1 (enabled) |
|
|
|
kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) |
|
for all guests. |
|
Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. |
|
|
|
kvm-arm.mode= |
|
[KVM,ARM] Select one of KVM/arm64's modes of operation. |
|
|
|
nvhe: Standard nVHE-based mode, without support for |
|
protected guests. |
|
|
|
protected: nVHE-based mode with support for guests whose |
|
state is kept private from the host. |
|
Not valid if the kernel is running in EL2. |
|
|
|
Defaults to VHE/nVHE based on hardware support. |
|
|
|
kvm-arm.vgic_v3_group0_trap= |
|
[KVM,ARM] Trap guest accesses to GICv3 group-0 |
|
system registers |
|
|
|
kvm-arm.vgic_v3_group1_trap= |
|
[KVM,ARM] Trap guest accesses to GICv3 group-1 |
|
system registers |
|
|
|
kvm-arm.vgic_v3_common_trap= |
|
[KVM,ARM] Trap guest accesses to GICv3 common |
|
system registers |
|
|
|
kvm-arm.vgic_v4_enable= |
|
[KVM,ARM] Allow use of GICv4 for direct injection of |
|
LPIs. |
|
|
|
kvm_cma_resv_ratio=n [PPC] |
|
Reserves given percentage from system memory area for |
|
contiguous memory allocation for KVM hash pagetable |
|
allocation. |
|
By default it reserves 5% of total system memory. |
|
Format: <integer> |
|
Default: 5 |
|
|
|
kvm-intel.ept= [KVM,Intel] Disable extended page tables |
|
(virtualized MMU) support on capable Intel chips. |
|
Default is 1 (enabled) |
|
|
|
kvm-intel.emulate_invalid_guest_state= |
|
[KVM,Intel] Enable emulation of invalid guest states |
|
Default is 0 (disabled) |
|
|
|
kvm-intel.flexpriority= |
|
[KVM,Intel] Disable FlexPriority feature (TPR shadow). |
|
Default is 1 (enabled) |
|
|
|
kvm-intel.nested= |
|
[KVM,Intel] Enable VMX nesting (nVMX). |
|
Default is 0 (disabled) |
|
|
|
kvm-intel.unrestricted_guest= |
|
[KVM,Intel] Disable unrestricted guest feature |
|
(virtualized real and unpaged mode) on capable |
|
Intel chips. Default is 1 (enabled) |
|
|
|
kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault |
|
CVE-2018-3620. |
|
|
|
Valid arguments: never, cond, always |
|
|
|
always: L1D cache flush on every VMENTER. |
|
cond: Flush L1D on VMENTER only when the code between |
|
VMEXIT and VMENTER can leak host memory. |
|
never: Disables the mitigation |
|
|
|
Default is cond (do L1 cache flush in specific instances) |
|
|
|
kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification |
|
feature (tagged TLBs) on capable Intel chips. |
|
Default is 1 (enabled) |
|
|
|
l1d_flush= [X86,INTEL] |
|
Control mitigation for L1D based snooping vulnerability. |
|
|
|
Certain CPUs are vulnerable to an exploit against CPU |
|
internal buffers which can forward information to a |
|
disclosure gadget under certain conditions. |
|
|
|
In vulnerable processors, the speculatively |
|
forwarded data can be used in a cache side channel |
|
attack, to access data to which the attacker does |
|
not have direct access. |
|
|
|
This parameter controls the mitigation. The |
|
options are: |
|
|
|
on - enable the interface for the mitigation |
|
|
|
l1tf= [X86] Control mitigation of the L1TF vulnerability on |
|
affected CPUs |
|
|
|
The kernel PTE inversion protection is unconditionally |
|
enabled and cannot be disabled. |
|
|
|
full |
|
Provides all available mitigations for the |
|
L1TF vulnerability. Disables SMT and |
|
enables all mitigations in the |
|
hypervisors, i.e. unconditional L1D flush. |
|
|
|
SMT control and L1D flush control via the |
|
sysfs interface is still possible after |
|
boot. Hypervisors will issue a warning |
|
when the first VM is started in a |
|
potentially insecure configuration, |
|
i.e. SMT enabled or L1D flush disabled. |
|
|
|
full,force |
|
Same as 'full', but disables SMT and L1D |
|
flush runtime control. Implies the |
|
'nosmt=force' command line option. |
|
(i.e. sysfs control of SMT is disabled.) |
|
|
|
flush |
|
Leaves SMT enabled and enables the default |
|
hypervisor mitigation, i.e. conditional |
|
L1D flush. |
|
|
|
SMT control and L1D flush control via the |
|
sysfs interface is still possible after |
|
boot. Hypervisors will issue a warning |
|
when the first VM is started in a |
|
potentially insecure configuration, |
|
i.e. SMT enabled or L1D flush disabled. |
|
|
|
flush,nosmt |
|
|
|
Disables SMT and enables the default |
|
hypervisor mitigation. |
|
|
|
SMT control and L1D flush control via the |
|
sysfs interface is still possible after |
|
boot. Hypervisors will issue a warning |
|
when the first VM is started in a |
|
potentially insecure configuration, |
|
i.e. SMT enabled or L1D flush disabled. |
|
|
|
flush,nowarn |
|
Same as 'flush', but hypervisors will not |
|
warn when a VM is started in a potentially |
|
insecure configuration. |
|
|
|
off |
|
Disables hypervisor mitigations and doesn't |
|
emit any warnings. |
|
It also drops the swap size and available |
|
RAM limit restriction on both hypervisor and |
|
bare metal. |
|
|
|
Default is 'flush'. |
|
|
|
For details see: Documentation/admin-guide/hw-vuln/l1tf.rst |
|
|
|
l2cr= [PPC] |
|
|
|
l3cr= [PPC] |
|
|
|
lapic [X86-32,APIC] Enable the local APIC even if BIOS |
|
disabled it. |
|
|
|
lapic= [X86,APIC] Do not use TSC deadline |
|
value for LAPIC timer one-shot implementation. Default |
|
back to the programmable timer unit in the LAPIC. |
|
Format: notscdeadline |
|
|
|
lapic_timer_c2_ok [X86,APIC] trust the local apic timer |
|
in C2 power state. |
|
|
|
libata.dma= [LIBATA] DMA control |
|
libata.dma=0 Disable all PATA and SATA DMA |
|
libata.dma=1 PATA and SATA Disk DMA only |
|
libata.dma=2 ATAPI (CDROM) DMA only |
|
libata.dma=4 Compact Flash DMA only |
|
Combinations also work, so libata.dma=3 enables DMA |
|
for disks and CDROMs, but not CFs. |
|
|
|
libata.ignore_hpa= [LIBATA] Ignore HPA limit |
|
libata.ignore_hpa=0 keep BIOS limits (default) |
|
libata.ignore_hpa=1 ignore limits, using full disk |
|
|
|
libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume |
|
when set. |
|
Format: <int> |
|
|
|
libata.force= [LIBATA] Force configurations. The format is comma- |
|
separated list of "[ID:]VAL" where ID is |
|
PORT[.DEVICE]. PORT and DEVICE are decimal numbers |
|
matching port, link or device. Basically, it matches |
|
the ATA ID string printed on console by libata. If |
|
the whole ID part is omitted, the last PORT and DEVICE |
|
values are used. If ID hasn't been specified yet, the |
|
configuration applies to all ports, links and devices. |
|
|
|
If only DEVICE is omitted, the parameter applies to |
|
the port and all links and devices behind it. DEVICE |
|
number of 0 either selects the first device or the |
|
first fan-out link behind PMP device. It does not |
|
select the host link. DEVICE number of 15 selects the |
|
host link and device attached to it. |
|
|
|
The VAL specifies the configuration to force. As long |
|
as there's no ambiguity shortcut notation is allowed. |
|
For example, both 1.5 and 1.5G would work for 1.5Gbps. |
|
The following configurations can be forced. |
|
|
|
* Cable type: 40c, 80c, short40c, unk, ign or sata. |
|
Any ID with matching PORT is used. |
|
|
|
* SATA link speed limit: 1.5Gbps or 3.0Gbps. |
|
|
|
* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. |
|
udma[/][16,25,33,44,66,100,133] notation is also |
|
allowed. |
|
|
|
* [no]ncq: Turn on or off NCQ. |
|
|
|
* [no]ncqtrim: Turn off queued DSM TRIM. |
|
|
|
* nohrst, nosrst, norst: suppress hard, soft |
|
and both resets. |
|
|
|
* rstonce: only attempt one reset during |
|
hot-unplug link recovery |
|
|
|
* dump_id: dump IDENTIFY data. |
|
|
|
* atapi_dmadir: Enable ATAPI DMADIR bridge support |
|
|
|
* disable: Disable this device. |
|
|
|
If there are multiple matching configurations changing |
|
the same attribute, the last one is used. |
|
|
|
memblock=debug [KNL] Enable memblock debug messages. |
|
|
|
load_ramdisk= [RAM] [Deprecated] |
|
|
|
lockd.nlm_grace_period=P [NFS] Assign grace period. |
|
Format: <integer> |
|
|
|
lockd.nlm_tcpport=N [NFS] Assign TCP port. |
|
Format: <integer> |
|
|
|
lockd.nlm_timeout=T [NFS] Assign timeout value. |
|
Format: <integer> |
|
|
|
lockd.nlm_udpport=M [NFS] Assign UDP port. |
|
Format: <integer> |
|
|
|
lockdown= [SECURITY] |
|
{ integrity | confidentiality } |
|
Enable the kernel lockdown feature. If set to |
|
integrity, kernel features that allow userland to |
|
modify the running kernel are disabled. If set to |
|
confidentiality, kernel features that allow userland |
|
to extract confidential information from the kernel |
|
are also disabled. |
|
|
|
locktorture.nreaders_stress= [KNL] |
|
Set the number of locking read-acquisition kthreads. |
|
Defaults to being automatically set based on the |
|
number of online CPUs. |
|
|
|
locktorture.nwriters_stress= [KNL] |
|
Set the number of locking write-acquisition kthreads. |
|
|
|
locktorture.onoff_holdoff= [KNL] |
|
Set time (s) after boot for CPU-hotplug testing. |
|
|
|
locktorture.onoff_interval= [KNL] |
|
Set time (s) between CPU-hotplug operations, or |
|
zero to disable CPU-hotplug testing. |
|
|
|
locktorture.shuffle_interval= [KNL] |
|
Set task-shuffle interval (jiffies). Shuffling |
|
tasks allows some CPUs to go into dyntick-idle |
|
mode during the locktorture test. |
|
|
|
locktorture.shutdown_secs= [KNL] |
|
Set time (s) after boot system shutdown. This |
|
is useful for hands-off automated testing. |
|
|
|
locktorture.stat_interval= [KNL] |
|
Time (s) between statistics printk()s. |
|
|
|
locktorture.stutter= [KNL] |
|
Time (s) to stutter testing, for example, |
|
specifying five seconds causes the test to run for |
|
five seconds, wait for five seconds, and so on. |
|
This tests the locking primitive's ability to |
|
transition abruptly to and from idle. |
|
|
|
locktorture.torture_type= [KNL] |
|
Specify the locking implementation to test. |
|
|
|
locktorture.verbose= [KNL] |
|
Enable additional printk() statements. |
|
|
|
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver |
|
Format: <irq> |
|
|
|
loglevel= All Kernel Messages with a loglevel smaller than the |
|
console loglevel will be printed to the console. It can |
|
also be changed with klogd or other programs. The |
|
loglevels are defined as follows: |
|
|
|
0 (KERN_EMERG) system is unusable |
|
1 (KERN_ALERT) action must be taken immediately |
|
2 (KERN_CRIT) critical conditions |
|
3 (KERN_ERR) error conditions |
|
4 (KERN_WARNING) warning conditions |
|
5 (KERN_NOTICE) normal but significant condition |
|
6 (KERN_INFO) informational |
|
7 (KERN_DEBUG) debug-level messages |
|
|
|
log_buf_len=n[KMG] Sets the size of the printk ring buffer, |
|
in bytes. n must be a power of two and greater |
|
than the minimal size. The minimal size is defined |
|
by LOG_BUF_SHIFT kernel config parameter. There is |
|
also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter |
|
that allows to increase the default size depending on |
|
the number of CPUs. See init/Kconfig for more details. |
|
|
|
logo.nologo [FB] Disables display of the built-in Linux logo. |
|
This may be used to provide more screen space for |
|
kernel log messages and is useful when debugging |
|
kernel boot problems. |
|
|
|
lp=0 [LP] Specify parallel ports to use, e.g, |
|
lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses |
|
lp=reset first parallel port). 'lp=0' disables the |
|
lp=auto printer driver. 'lp=reset' (which can be |
|
specified in addition to the ports) causes |
|
attached printers to be reset. Using |
|
lp=port1,port2,... specifies the parallel ports |
|
to associate lp devices with, starting with |
|
lp0. A port specification may be 'none' to skip |
|
that lp device, or a parport name such as |
|
'parport0'. Specifying 'lp=auto' instead of a |
|
port specification list means that device IDs |
|
from each port should be examined, to see if |
|
an IEEE 1284-compliant printer is attached; if |
|
so, the driver will manage that printer. |
|
See also header of drivers/char/lp.c. |
|
|
|
lpj=n [KNL] |
|
Sets loops_per_jiffy to given constant, thus avoiding |
|
time-consuming boot-time autodetection (up to 250 ms per |
|
CPU). 0 enables autodetection (default). To determine |
|
the correct value for your kernel, boot with normal |
|
autodetection and see what value is printed. Note that |
|
on SMP systems the preset will be applied to all CPUs, |
|
which is likely to cause problems if your CPUs need |
|
significantly divergent settings. An incorrect value |
|
will cause delays in the kernel to be wrong, leading to |
|
unpredictable I/O errors and other breakage. Although |
|
unlikely, in the extreme case this might damage your |
|
hardware. |
|
|
|
ltpc= [NET] |
|
Format: <io>,<irq>,<dma> |
|
|
|
lsm.debug [SECURITY] Enable LSM initialization debugging output. |
|
|
|
lsm=lsm1,...,lsmN |
|
[SECURITY] Choose order of LSM initialization. This |
|
overrides CONFIG_LSM, and the "security=" parameter. |
|
|
|
machvec= [IA-64] Force the use of a particular machine-vector |
|
(machvec) in a generic kernel. |
|
Example: machvec=hpzx1 |
|
|
|
machtype= [Loongson] Share the same kernel image file between |
|
different yeeloong laptops. |
|
Example: machtype=lemote-yeeloong-2f-7inch |
|
|
|
max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater |
|
than or equal to this physical address is ignored. |
|
|
|
maxcpus= [SMP] Maximum number of processors that an SMP kernel |
|
will bring up during bootup. maxcpus=n : n >= 0 limits |
|
the kernel to bring up 'n' processors. Surely after |
|
bootup you can bring up the other plugged cpu by executing |
|
"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus |
|
only takes effect during system bootup. |
|
While n=0 is a special case, it is equivalent to "nosmp", |
|
which also disables the IO APIC. |
|
|
|
max_loop= [LOOP] The number of loop block devices that get |
|
(loop.max_loop) unconditionally pre-created at init time. The default |
|
number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead |
|
of statically allocating a predefined number, loop |
|
devices can be requested on-demand with the |
|
/dev/loop-control interface. |
|
|
|
mce [X86-32] Machine Check Exception |
|
|
|
mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst |
|
|
|
md= [HW] RAID subsystems devices and level |
|
See Documentation/admin-guide/md.rst. |
|
|
|
mdacon= [MDA] |
|
Format: <first>,<last> |
|
Specifies range of consoles to be captured by the MDA. |
|
|
|
mds= [X86,INTEL] |
|
Control mitigation for the Micro-architectural Data |
|
Sampling (MDS) vulnerability. |
|
|
|
Certain CPUs are vulnerable to an exploit against CPU |
|
internal buffers which can forward information to a |
|
disclosure gadget under certain conditions. |
|
|
|
In vulnerable processors, the speculatively |
|
forwarded data can be used in a cache side channel |
|
attack, to access data to which the attacker does |
|
not have direct access. |
|
|
|
This parameter controls the MDS mitigation. The |
|
options are: |
|
|
|
full - Enable MDS mitigation on vulnerable CPUs |
|
full,nosmt - Enable MDS mitigation and disable |
|
SMT on vulnerable CPUs |
|
off - Unconditionally disable MDS mitigation |
|
|
|
On TAA-affected machines, mds=off can be prevented by |
|
an active TAA mitigation as both vulnerabilities are |
|
mitigated with the same mechanism so in order to disable |
|
this mitigation, you need to specify tsx_async_abort=off |
|
too. |
|
|
|
Not specifying this option is equivalent to |
|
mds=full. |
|
|
|
For details see: Documentation/admin-guide/hw-vuln/mds.rst |
|
|
|
mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
|
Amount of memory to be used in cases as follows: |
|
|
|
1 for test; |
|
2 when the kernel is not able to see the whole system memory; |
|
3 memory that lies after 'mem=' boundary is excluded from |
|
the hypervisor, then assigned to KVM guests. |
|
|
|
[X86] Work as limiting max address. Use together |
|
with memmap= to avoid physical address space collisions. |
|
Without memmap= PCI devices could be placed at addresses |
|
belonging to unused RAM. |
|
|
|
Note that this only takes effects during boot time since |
|
in above case 3, memory may need be hot added after boot |
|
if system memory of hypervisor is not sufficient. |
|
|
|
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
|
memory. |
|
|
|
memchunk=nn[KMG] |
|
[KNL,SH] Allow user to override the default size for |
|
per-device physically contiguous DMA buffers. |
|
|
|
memhp_default_state=online/offline |
|
[KNL] Set the initial state for the memory hotplug |
|
onlining policy. If not specified, the default value is |
|
set according to the |
|
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config |
|
option. |
|
See Documentation/admin-guide/mm/memory-hotplug.rst. |
|
|
|
memmap=exactmap [KNL,X86] Enable setting of an exact |
|
E820 memory map, as specified by the user. |
|
Such memmap=exactmap lines can be constructed based on |
|
BIOS output or other requirements. See the memmap=nn@ss |
|
option description. |
|
|
|
memmap=nn[KMG]@ss[KMG] |
|
[KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory. |
|
Region of memory to be used is from ss to ss+nn. |
|
If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], |
|
which limits max address to nn[KMG]. |
|
Multiple different regions can be specified, |
|
comma delimited. |
|
Example: |
|
memmap=100M@2G,100M#3G,1G!1024G |
|
|
|
memmap=nn[KMG]#ss[KMG] |
|
[KNL,ACPI] Mark specific memory as ACPI data. |
|
Region of memory to be marked is from ss to ss+nn. |
|
|
|
memmap=nn[KMG]$ss[KMG] |
|
[KNL,ACPI] Mark specific memory as reserved. |
|
Region of memory to be reserved is from ss to ss+nn. |
|
Example: Exclude memory from 0x18690000-0x1869ffff |
|
memmap=64K$0x18690000 |
|
or |
|
memmap=0x10000$0x18690000 |
|
Some bootloaders may need an escape character before '$', |
|
like Grub2, otherwise '$' and the following number |
|
will be eaten. |
|
|
|
memmap=nn[KMG]!ss[KMG] |
|
[KNL,X86] Mark specific memory as protected. |
|
Region of memory to be used, from ss to ss+nn. |
|
The memory region may be marked as e820 type 12 (0xc) |
|
and is NVDIMM or ADR memory. |
|
|
|
memmap=<size>%<offset>-<oldtype>+<newtype> |
|
[KNL,ACPI] Convert memory within the specified region |
|
from <oldtype> to <newtype>. If "-<oldtype>" is left |
|
out, the whole region will be marked as <newtype>, |
|
even if previously unavailable. If "+<newtype>" is left |
|
out, matching memory will be removed. Types are |
|
specified as e820 types, e.g., 1 = RAM, 2 = reserved, |
|
3 = ACPI, 12 = PRAM. |
|
|
|
memory_corruption_check=0/1 [X86] |
|
Some BIOSes seem to corrupt the first 64k of |
|
memory when doing things like suspend/resume. |
|
Setting this option will scan the memory |
|
looking for corruption. Enabling this will |
|
both detect corruption and prevent the kernel |
|
from using the memory being corrupted. |
|
However, its intended as a diagnostic tool; if |
|
repeatable BIOS-originated corruption always |
|
affects the same memory, you can use memmap= |
|
to prevent the kernel from using that memory. |
|
|
|
memory_corruption_check_size=size [X86] |
|
By default it checks for corruption in the low |
|
64k, making this memory unavailable for normal |
|
use. Use this parameter to scan for |
|
corruption in more or less memory. |
|
|
|
memory_corruption_check_period=seconds [X86] |
|
By default it checks for corruption every 60 |
|
seconds. Use this parameter to check at some |
|
other rate. 0 disables periodic checking. |
|
|
|
memory_hotplug.memmap_on_memory |
|
[KNL,X86,ARM] Boolean flag to enable this feature. |
|
Format: {on | off (default)} |
|
When enabled, runtime hotplugged memory will |
|
allocate its internal metadata (struct pages) |
|
from the hotadded memory which will allow to |
|
hotadd a lot of memory without requiring |
|
additional memory to do so. |
|
This feature is disabled by default because it |
|
has some implication on large (e.g. GB) |
|
allocations in some configurations (e.g. small |
|
memory blocks). |
|
The state of the flag can be read in |
|
/sys/module/memory_hotplug/parameters/memmap_on_memory. |
|
Note that even when enabled, there are a few cases where |
|
the feature is not effective. |
|
|
|
This is not compatible with hugetlb_free_vmemmap. If |
|
both parameters are enabled, hugetlb_free_vmemmap takes |
|
precedence over memory_hotplug.memmap_on_memory. |
|
|
|
memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest |
|
Format: <integer> |
|
default : 0 <disable> |
|
Specifies the number of memtest passes to be |
|
performed. Each pass selects another test |
|
pattern from a given set of patterns. Memtest |
|
fills the memory with this pattern, validates |
|
memory contents and reserves bad memory |
|
regions that are detected. |
|
|
|
mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control |
|
Valid arguments: on, off |
|
Default (depends on kernel configuration option): |
|
on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) |
|
off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) |
|
mem_encrypt=on: Activate SME |
|
mem_encrypt=off: Do not activate SME |
|
|
|
Refer to Documentation/virt/kvm/amd-memory-encryption.rst |
|
for details on when memory encryption can be activated. |
|
|
|
mem_sleep_default= [SUSPEND] Default system suspend mode: |
|
s2idle - Suspend-To-Idle |
|
shallow - Power-On Suspend or equivalent (if supported) |
|
deep - Suspend-To-RAM or equivalent (if supported) |
|
See Documentation/admin-guide/pm/sleep-states.rst. |
|
|
|
meye.*= [HW] Set MotionEye Camera parameters |
|
See Documentation/admin-guide/media/meye.rst. |
|
|
|
mfgpt_irq= [IA-32] Specify the IRQ to use for the |
|
Multi-Function General Purpose Timers on AMD Geode |
|
platforms. |
|
|
|
mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when |
|
the BIOS has incorrectly applied a workaround. TinyBIOS |
|
version 0.98 is known to be affected, 0.99 fixes the |
|
problem by letting the user disable the workaround. |
|
|
|
mga= [HW,DRM] |
|
|
|
min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this |
|
physical address is ignored. |
|
|
|
mini2440= [ARM,HW,KNL] |
|
Format:[0..2][b][c][t] |
|
Default: "0tb" |
|
MINI2440 configuration specification: |
|
0 - The attached screen is the 3.5" TFT |
|
1 - The attached screen is the 7" TFT |
|
2 - The VGA Shield is attached (1024x768) |
|
Leaving out the screen size parameter will not load |
|
the TFT driver, and the framebuffer will be left |
|
unconfigured. |
|
b - Enable backlight. The TFT backlight pin will be |
|
linked to the kernel VESA blanking code and a GPIO |
|
LED. This parameter is not necessary when using the |
|
VGA shield. |
|
c - Enable the s3c camera interface. |
|
t - Reserved for enabling touchscreen support. The |
|
touchscreen support is not enabled in the mainstream |
|
kernel as of 2.6.30, a preliminary port can be found |
|
in the "bleeding edge" mini2440 support kernel at |
|
https://repo.or.cz/w/linux-2.6/mini2440.git |
|
|
|
mitigations= |
|
[X86,PPC,S390,ARM64] Control optional mitigations for |
|
CPU vulnerabilities. This is a set of curated, |
|
arch-independent options, each of which is an |
|
aggregation of existing arch-specific options. |
|
|
|
off |
|
Disable all optional CPU mitigations. This |
|
improves system performance, but it may also |
|
expose users to several CPU vulnerabilities. |
|
Equivalent to: nopti [X86,PPC] |
|
kpti=0 [ARM64] |
|
nospectre_v1 [X86,PPC] |
|
nobp=0 [S390] |
|
nospectre_v2 [X86,PPC,S390,ARM64] |
|
spectre_v2_user=off [X86] |
|
spec_store_bypass_disable=off [X86,PPC] |
|
ssbd=force-off [ARM64] |
|
l1tf=off [X86] |
|
mds=off [X86] |
|
tsx_async_abort=off [X86] |
|
kvm.nx_huge_pages=off [X86] |
|
no_entry_flush [PPC] |
|
no_uaccess_flush [PPC] |
|
|
|
Exceptions: |
|
This does not have any effect on |
|
kvm.nx_huge_pages when |
|
kvm.nx_huge_pages=force. |
|
|
|
auto (default) |
|
Mitigate all CPU vulnerabilities, but leave SMT |
|
enabled, even if it's vulnerable. This is for |
|
users who don't want to be surprised by SMT |
|
getting disabled across kernel upgrades, or who |
|
have other ways of avoiding SMT-based attacks. |
|
Equivalent to: (default behavior) |
|
|
|
auto,nosmt |
|
Mitigate all CPU vulnerabilities, disabling SMT |
|
if needed. This is for users who always want to |
|
be fully mitigated, even if it means losing SMT. |
|
Equivalent to: l1tf=flush,nosmt [X86] |
|
mds=full,nosmt [X86] |
|
tsx_async_abort=full,nosmt [X86] |
|
|
|
mminit_loglevel= |
|
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this |
|
parameter allows control of the logging verbosity for |
|
the additional memory initialisation checks. A value |
|
of 0 disables mminit logging and a level of 4 will |
|
log everything. Information is printed at KERN_DEBUG |
|
so loglevel=8 may also need to be specified. |
|
|
|
module.sig_enforce |
|
[KNL] When CONFIG_MODULE_SIG is set, this means that |
|
modules without (valid) signatures will fail to load. |
|
Note that if CONFIG_MODULE_SIG_FORCE is set, that |
|
is always true, so this option does nothing. |
|
|
|
module_blacklist= [KNL] Do not load a comma-separated list of |
|
modules. Useful for debugging problem modules. |
|
|
|
mousedev.tap_time= |
|
[MOUSE] Maximum time between finger touching and |
|
leaving touchpad surface for touch to be considered |
|
a tap and be reported as a left button click (for |
|
touchpads working in absolute mode only). |
|
Format: <msecs> |
|
mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices |
|
reporting absolute coordinates, such as tablets |
|
mousedev.yres= [MOUSE] Vertical screen resolution, used for devices |
|
reporting absolute coordinates, such as tablets |
|
|
|
movablecore= [KNL,X86,IA-64,PPC] |
|
Format: nn[KMGTPE] | nn% |
|
This parameter is the complement to kernelcore=, it |
|
specifies the amount of memory used for migratable |
|
allocations. If both kernelcore and movablecore is |
|
specified, then kernelcore will be at *least* the |
|
specified value but may be more. If movablecore on its |
|
own is specified, the administrator must be careful |
|
that the amount of memory usable for all allocations |
|
is not too small. |
|
|
|
movable_node [KNL] Boot-time switch to make hotplugable memory |
|
NUMA nodes to be movable. This means that the memory |
|
of such nodes will be usable only for movable |
|
allocations which rules out almost all kernel |
|
allocations. Use with caution! |
|
|
|
MTD_Partition= [MTD] |
|
Format: <name>,<region-number>,<size>,<offset> |
|
|
|
MTD_Region= [MTD] Format: |
|
<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] |
|
|
|
mtdparts= [MTD] |
|
See drivers/mtd/parsers/cmdlinepart.c |
|
|
|
multitce=off [PPC] This parameter disables the use of the pSeries |
|
firmware feature for updating multiple TCE entries |
|
at a time. |
|
|
|
onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration |
|
|
|
Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] |
|
|
|
boundary - index of last SLC block on Flex-OneNAND. |
|
The remaining blocks are configured as MLC blocks. |
|
lock - Configure if Flex-OneNAND boundary should be locked. |
|
Once locked, the boundary cannot be changed. |
|
1 indicates lock status, 0 indicates unlock status. |
|
|
|
mtdset= [ARM] |
|
ARM/S3C2412 JIVE boot control |
|
|
|
See arch/arm/mach-s3c/mach-jive.c |
|
|
|
mtouchusb.raw_coordinates= |
|
[HW] Make the MicroTouch USB driver use raw coordinates |
|
('y', default) or cooked coordinates ('n') |
|
|
|
mtrr_chunk_size=nn[KMG] [X86] |
|
used for mtrr cleanup. It is largest continuous chunk |
|
that could hold holes aka. UC entries. |
|
|
|
mtrr_gran_size=nn[KMG] [X86] |
|
Used for mtrr cleanup. It is granularity of mtrr block. |
|
Default is 1. |
|
Large value could prevent small alignment from |
|
using up MTRRs. |
|
|
|
mtrr_spare_reg_nr=n [X86] |
|
Format: <integer> |
|
Range: 0,7 : spare reg number |
|
Default : 1 |
|
Used for mtrr cleanup. It is spare mtrr entries number. |
|
Set to 2 or more if your graphical card needs more. |
|
|
|
n2= [NET] SDL Inc. RISCom/N2 synchronous serial card |
|
|
|
netdev= [NET] Network devices parameters |
|
Format: <irq>,<io>,<mem_start>,<mem_end>,<name> |
|
Note that mem_start is often overloaded to mean |
|
something different and driver-specific. |
|
This usage is only documented in each driver source |
|
file if at all. |
|
|
|
nf_conntrack.acct= |
|
[NETFILTER] Enable connection tracking flow accounting |
|
0 to disable accounting |
|
1 to enable accounting |
|
Default value is 0. |
|
|
|
nfsaddrs= [NFS] Deprecated. Use ip= instead. |
|
See Documentation/admin-guide/nfs/nfsroot.rst. |
|
|
|
nfsroot= [NFS] nfs root filesystem for disk-less boxes. |
|
See Documentation/admin-guide/nfs/nfsroot.rst. |
|
|
|
nfsrootdebug [NFS] enable nfsroot debugging messages. |
|
See Documentation/admin-guide/nfs/nfsroot.rst. |
|
|
|
nfs.callback_nr_threads= |
|
[NFSv4] set the total number of threads that the |
|
NFS client will assign to service NFSv4 callback |
|
requests. |
|
|
|
nfs.callback_tcpport= |
|
[NFS] set the TCP port on which the NFSv4 callback |
|
channel should listen. |
|
|
|
nfs.cache_getent= |
|
[NFS] sets the pathname to the program which is used |
|
to update the NFS client cache entries. |
|
|
|
nfs.cache_getent_timeout= |
|
[NFS] sets the timeout after which an attempt to |
|
update a cache entry is deemed to have failed. |
|
|
|
nfs.idmap_cache_timeout= |
|
[NFS] set the maximum lifetime for idmapper cache |
|
entries. |
|
|
|
nfs.enable_ino64= |
|
[NFS] enable 64-bit inode numbers. |
|
If zero, the NFS client will fake up a 32-bit inode |
|
number for the readdir() and stat() syscalls instead |
|
of returning the full 64-bit number. |
|
The default is to return 64-bit inode numbers. |
|
|
|
nfs.max_session_cb_slots= |
|
[NFSv4.1] Sets the maximum number of session |
|
slots the client will assign to the callback |
|
channel. This determines the maximum number of |
|
callbacks the client will process in parallel for |
|
a particular server. |
|
|
|
nfs.max_session_slots= |
|
[NFSv4.1] Sets the maximum number of session slots |
|
the client will attempt to negotiate with the server. |
|
This limits the number of simultaneous RPC requests |
|
that the client can send to the NFSv4.1 server. |
|
Note that there is little point in setting this |
|
value higher than the max_tcp_slot_table_limit. |
|
|
|
nfs.nfs4_disable_idmapping= |
|
[NFSv4] When set to the default of '1', this option |
|
ensures that both the RPC level authentication |
|
scheme and the NFS level operations agree to use |
|
numeric uids/gids if the mount is using the |
|
'sec=sys' security flavour. In effect it is |
|
disabling idmapping, which can make migration from |
|
legacy NFSv2/v3 systems to NFSv4 easier. |
|
Servers that do not support this mode of operation |
|
will be autodetected by the client, and it will fall |
|
back to using the idmapper. |
|
To turn off this behaviour, set the value to '0'. |
|
nfs.nfs4_unique_id= |
|
[NFS4] Specify an additional fixed unique ident- |
|
ification string that NFSv4 clients can insert into |
|
their nfs_client_id4 string. This is typically a |
|
UUID that is generated at system install time. |
|
|
|
nfs.send_implementation_id = |
|
[NFSv4.1] Send client implementation identification |
|
information in exchange_id requests. |
|
If zero, no implementation identification information |
|
will be sent. |
|
The default is to send the implementation identification |
|
information. |
|
|
|
nfs.recover_lost_locks = |
|
[NFSv4] Attempt to recover locks that were lost due |
|
to a lease timeout on the server. Please note that |
|
doing this risks data corruption, since there are |
|
no guarantees that the file will remain unchanged |
|
after the locks are lost. |
|
If you want to enable the kernel legacy behaviour of |
|
attempting to recover these locks, then set this |
|
parameter to '1'. |
|
The default parameter value of '0' causes the kernel |
|
not to attempt recovery of lost locks. |
|
|
|
nfs4.layoutstats_timer = |
|
[NFSv4.2] Change the rate at which the kernel sends |
|
layoutstats to the pNFS metadata server. |
|
|
|
Setting this to value to 0 causes the kernel to use |
|
whatever value is the default set by the layout |
|
driver. A non-zero value sets the minimum interval |
|
in seconds between layoutstats transmissions. |
|
|
|
nfsd.nfs4_disable_idmapping= |
|
[NFSv4] When set to the default of '1', the NFSv4 |
|
server will return only numeric uids and gids to |
|
clients using auth_sys, and will accept numeric uids |
|
and gids from such clients. This is intended to ease |
|
migration from NFSv2/v3. |
|
|
|
nmi_backtrace.backtrace_idle [KNL] |
|
Dump stacks even of idle CPUs in response to an |
|
NMI stack-backtrace request. |
|
|
|
nmi_debug= [KNL,SH] Specify one or more actions to take |
|
when a NMI is triggered. |
|
Format: [state][,regs][,debounce][,die] |
|
|
|
nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels |
|
Format: [panic,][nopanic,][num] |
|
Valid num: 0 or 1 |
|
0 - turn hardlockup detector in nmi_watchdog off |
|
1 - turn hardlockup detector in nmi_watchdog on |
|
When panic is specified, panic when an NMI watchdog |
|
timeout occurs (or 'nopanic' to not panic on an NMI |
|
watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) |
|
To disable both hard and soft lockup detectors, |
|
please see 'nowatchdog'. |
|
This is useful when you use a panic=... timeout and |
|
need the box quickly up again. |
|
|
|
These settings can be accessed at runtime via |
|
the nmi_watchdog and hardlockup_panic sysctls. |
|
|
|
netpoll.carrier_timeout= |
|
[NET] Specifies amount of time (in seconds) that |
|
netpoll should wait for a carrier. By default netpoll |
|
waits 4 seconds. |
|
|
|
no387 [BUGS=X86-32] Tells the kernel to use the 387 maths |
|
emulation library even if a 387 maths coprocessor |
|
is present. |
|
|
|
no5lvl [X86-64] Disable 5-level paging mode. Forces |
|
kernel to use 4-level paging instead. |
|
|
|
nofsgsbase [X86] Disables FSGSBASE instructions. |
|
|
|
no_console_suspend |
|
[HW] Never suspend the console |
|
Disable suspending of consoles during suspend and |
|
hibernate operations. Once disabled, debugging |
|
messages can reach various consoles while the rest |
|
of the system is being put to sleep (ie, while |
|
debugging driver suspend/resume hooks). This may |
|
not work reliably with all consoles, but is known |
|
to work with serial and VGA consoles. |
|
To facilitate more flexible debugging, we also add |
|
console_suspend, a printk module parameter to control |
|
it. Users could use console_suspend (usually |
|
/sys/module/printk/parameters/console_suspend) to |
|
turn on/off it dynamically. |
|
|
|
novmcoredd [KNL,KDUMP] |
|
Disable device dump. Device dump allows drivers to |
|
append dump data to vmcore so you can collect driver |
|
specified debug info. Drivers can append the data |
|
without any limit and this data is stored in memory, |
|
so this may cause significant memory stress. Disabling |
|
device dump can help save memory but the driver debug |
|
data will be no longer available. This parameter |
|
is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP |
|
is set. |
|
|
|
noaliencache [MM, NUMA, SLAB] Disables the allocation of alien |
|
caches in the slab allocator. Saves per-node memory, |
|
but will impact performance. |
|
|
|
noalign [KNL,ARM] |
|
|
|
noaltinstr [S390] Disables alternative instructions patching |
|
(CPU alternatives feature). |
|
|
|
noapic [SMP,APIC] Tells the kernel to not make use of any |
|
IOAPICs that may be present in the system. |
|
|
|
noautogroup Disable scheduler automatic task group creation. |
|
|
|
nobats [PPC] Do not use BATs for mapping kernel lowmem |
|
on "Classic" PPC cores. |
|
|
|
nocache [ARM] |
|
|
|
noclflush [BUGS=X86] Don't use the CLFLUSH instruction |
|
|
|
delayacct [KNL] Enable per-task delay accounting |
|
|
|
nodsp [SH] Disable hardware DSP at boot time. |
|
|
|
noefi Disable EFI runtime services support. |
|
|
|
no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel. |
|
|
|
noexec [IA-64] |
|
|
|
noexec [X86] |
|
On X86-32 available only on PAE configured kernels. |
|
noexec=on: enable non-executable mappings (default) |
|
noexec=off: disable non-executable mappings |
|
|
|
nosmap [X86,PPC] |
|
Disable SMAP (Supervisor Mode Access Prevention) |
|
even if it is supported by processor. |
|
|
|
nosmep [X86,PPC] |
|
Disable SMEP (Supervisor Mode Execution Prevention) |
|
even if it is supported by processor. |
|
|
|
noexec32 [X86-64] |
|
This affects only 32-bit executables. |
|
noexec32=on: enable non-executable mappings (default) |
|
read doesn't imply executable mappings |
|
noexec32=off: disable non-executable mappings |
|
read implies executable mappings |
|
|
|
nofpu [MIPS,SH] Disable hardware FPU at boot time. |
|
|
|
nofxsr [BUGS=X86-32] Disables x86 floating point extended |
|
register save and restore. The kernel will only save |
|
legacy floating-point registers on task switch. |
|
|
|
nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. |
|
|
|
nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. |
|
|
|
nosmt [KNL,S390] Disable symmetric multithreading (SMT). |
|
Equivalent to smt=1. |
|
|
|
[KNL,X86] Disable symmetric multithreading (SMT). |
|
nosmt=force: Force disable SMT, cannot be undone |
|
via the sysfs control file. |
|
|
|
nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 |
|
(bounds check bypass). With this option data leaks are |
|
possible in the system. |
|
|
|
nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for |
|
the Spectre variant 2 (indirect branch prediction) |
|
vulnerability. System may allow data leaks with this |
|
option. |
|
|
|
nospec_store_bypass_disable |
|
[HW] Disable all mitigations for the Speculative Store Bypass vulnerability |
|
|
|
no_uaccess_flush |
|
[PPC] Don't flush the L1-D cache after accessing user data. |
|
|
|
noxsave [BUGS=X86] Disables x86 extended register state save |
|
and restore using xsave. The kernel will fallback to |
|
enabling legacy floating-point and sse state. |
|
|
|
noxsaveopt [X86] Disables xsaveopt used in saving x86 extended |
|
register states. The kernel will fall back to use |
|
xsave to save the states. By using this parameter, |
|
performance of saving the states is degraded because |
|
xsave doesn't support modified optimization while |
|
xsaveopt supports it on xsaveopt enabled systems. |
|
|
|
noxsaves [X86] Disables xsaves and xrstors used in saving and |
|
restoring x86 extended register state in compacted |
|
form of xsave area. The kernel will fall back to use |
|
xsaveopt and xrstor to save and restore the states |
|
in standard form of xsave area. By using this |
|
parameter, xsave area per process might occupy more |
|
memory on xsaves enabled systems. |
|
|
|
nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait |
|
in do_idle() and not use the arch_cpu_idle() |
|
implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP |
|
to be effective. This is useful on platforms where the |
|
sleep(SH) or wfi(ARM,ARM64) instructions do not work |
|
correctly or when doing power measurements to evalute |
|
the impact of the sleep instructions. This is also |
|
useful when using JTAG debugger. |
|
|
|
no_file_caps Tells the kernel not to honor file capabilities. The |
|
only way then for a file to be executed with privilege |
|
is to be setuid root or executed by root. |
|
|
|
nohalt [IA-64] Tells the kernel not to use the power saving |
|
function PAL_HALT_LIGHT when idle. This increases |
|
power-consumption. On the positive side, it reduces |
|
interrupt wake-up latency, which may improve performance |
|
in certain environments such as networked servers or |
|
real-time systems. |
|
|
|
no_hash_pointers |
|
Force pointers printed to the console or buffers to be |
|
unhashed. By default, when a pointer is printed via %p |
|
format string, that pointer is "hashed", i.e. obscured |
|
by hashing the pointer value. This is a security feature |
|
that hides actual kernel addresses from unprivileged |
|
users, but it also makes debugging the kernel more |
|
difficult since unequal pointers can no longer be |
|
compared. However, if this command-line option is |
|
specified, then all normal pointers will have their true |
|
value printed. Pointers printed via %pK may still be |
|
hashed. This option should only be specified when |
|
debugging the kernel. Please do not use on production |
|
kernels. |
|
|
|
nohibernate [HIBERNATION] Disable hibernation and resume. |
|
|
|
nohz= [KNL] Boottime enable/disable dynamic ticks |
|
Valid arguments: on, off |
|
Default: on |
|
|
|
nohz_full= [KNL,BOOT,SMP,ISOL] |
|
The argument is a cpu list, as described above. |
|
In kernels built with CONFIG_NO_HZ_FULL=y, set |
|
the specified list of CPUs whose tick will be stopped |
|
whenever possible. The boot CPU will be forced outside |
|
the range to maintain the timekeeping. Any CPUs |
|
in this list will have their RCU callbacks offloaded, |
|
just as if they had also been called out in the |
|
rcu_nocbs= boot parameter. |
|
|
|
noiotrap [SH] Disables trapped I/O port accesses. |
|
|
|
noirqdebug [X86-32] Disables the code which attempts to detect and |
|
disable unhandled interrupt sources. |
|
|
|
no_timer_check [X86,APIC] Disables the code which tests for |
|
broken timer IRQ sources. |
|
|
|
noisapnp [ISAPNP] Disables ISA PnP code. |
|
|
|
noinitrd [RAM] Tells the kernel not to load any configured |
|
initial RAM disk. |
|
|
|
nointremap [X86-64, Intel-IOMMU] Do not enable interrupt |
|
remapping. |
|
[Deprecated - use intremap=off] |
|
|
|
nointroute [IA-64] |
|
|
|
noinvpcid [X86] Disable the INVPCID cpu feature. |
|
|
|
nojitter [IA-64] Disables jitter checking for ITC timers. |
|
|
|
no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver |
|
|
|
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page |
|
fault handling. |
|
|
|
no-vmw-sched-clock |
|
[X86,PV_OPS] Disable paravirtualized VMware scheduler |
|
clock and use the default one. |
|
|
|
no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time |
|
accounting. steal time is computed, but won't |
|
influence scheduler behaviour |
|
|
|
nolapic [X86-32,APIC] Do not enable or use the local APIC. |
|
|
|
nolapic_timer [X86-32,APIC] Do not use the local APIC timer. |
|
|
|
noltlbs [PPC] Do not use large page/tlb entries for kernel |
|
lowmem mapping on PPC40x and PPC8xx |
|
|
|
nomca [IA-64] Disable machine check abort handling |
|
|
|
nomce [X86-32] Disable Machine Check Exception |
|
|
|
nomfgpt [X86-32] Disable Multi-Function General Purpose |
|
Timer usage (for AMD Geode machines). |
|
|
|
nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to |
|
shutdown the other cpus. Instead use the REBOOT_VECTOR |
|
irq. |
|
|
|
nomodule Disable module load |
|
|
|
nopat [X86] Disable PAT (page attribute table extension of |
|
pagetables) support. |
|
|
|
nopcid [X86-64] Disable the PCID cpu feature. |
|
|
|
norandmaps Don't use address space randomization. Equivalent to |
|
echo 0 > /proc/sys/kernel/randomize_va_space |
|
|
|
noreplace-smp [X86-32,SMP] Don't replace SMP instructions |
|
with UP alternatives |
|
|
|
nordrand [X86] Disable kernel use of the RDRAND and |
|
RDSEED instructions even if they are supported |
|
by the processor. RDRAND and RDSEED are still |
|
available to user space applications. |
|
|
|
noresume [SWSUSP] Disables resume and restores original swap |
|
space. |
|
|
|
no-scroll [VGA] Disables scrollback. |
|
This is required for the Braillex ib80-piezo Braille |
|
reader made by F.H. Papenmeier (Germany). |
|
|
|
nosbagart [IA-64] |
|
|
|
nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. |
|
|
|
nosgx [X86-64,SGX] Disables Intel SGX kernel support. |
|
|
|
nosmp [SMP] Tells an SMP kernel to act as a UP kernel, |
|
and disable the IO APIC. legacy for "maxcpus=0". |
|
|
|
nosoftlockup [KNL] Disable the soft-lockup detector. |
|
|
|
nosync [HW,M68K] Disables sync negotiation for all devices. |
|
|
|
nowatchdog [KNL] Disable both lockup detectors, i.e. |
|
soft-lockup and NMI watchdog (hard-lockup). |
|
|
|
nowb [ARM] |
|
|
|
nox2apic [X86-64,APIC] Do not enable x2APIC mode. |
|
|
|
cpu0_hotplug [X86] Turn on CPU0 hotplug feature when |
|
CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. |
|
Some features depend on CPU0. Known dependencies are: |
|
1. Resume from suspend/hibernate depends on CPU0. |
|
Suspend/hibernate will fail if CPU0 is offline and you |
|
need to online CPU0 before suspend/hibernate. |
|
2. PIC interrupts also depend on CPU0. CPU0 can't be |
|
removed if a PIC interrupt is detected. |
|
It's said poweroff/reboot may depend on CPU0 on some |
|
machines although I haven't seen such issues so far |
|
after CPU0 is offline on a few tested machines. |
|
If the dependencies are under your control, you can |
|
turn on cpu0_hotplug. |
|
|
|
nps_mtm_hs_ctr= [KNL,ARC] |
|
This parameter sets the maximum duration, in |
|
cycles, each HW thread of the CTOP can run |
|
without interruptions, before HW switches it. |
|
The actual maximum duration is 16 times this |
|
parameter's value. |
|
Format: integer between 1 and 255 |
|
Default: 255 |
|
|
|
nptcg= [IA-64] Override max number of concurrent global TLB |
|
purges which is reported from either PAL_VM_SUMMARY or |
|
SAL PALO. |
|
|
|
nr_cpus= [SMP] Maximum number of processors that an SMP kernel |
|
could support. nr_cpus=n : n >= 1 limits the kernel to |
|
support 'n' processors. It could be larger than the |
|
number of already plugged CPU during bootup, later in |
|
runtime you can physically add extra cpu until it reaches |
|
n. So during boot up some boot time memory for per-cpu |
|
variables need be pre-allocated for later physical cpu |
|
hot plugging. |
|
|
|
nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
|
|
|
numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only |
|
set up a single NUMA node spanning all memory. |
|
|
|
numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic |
|
NUMA balancing. |
|
Allowed values are enable and disable |
|
|
|
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
|
'node', 'default' can be specified |
|
This can be set from sysctl after boot. |
|
See Documentation/admin-guide/sysctl/vm.rst for details. |
|
|
|
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
|
See Documentation/core-api/debugging-via-ohci1394.rst for more |
|
info. |
|
|
|
olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
|
Rather than timing out after 20 ms if an EC |
|
command is not properly ACKed, override the length |
|
of the timeout. We have interrupts disabled while |
|
waiting for the ACK, so if this is set too high |
|
interrupts *may* be lost! |
|
|
|
omap_mux= [OMAP] Override bootloader pin multiplexing. |
|
Format: <mux_mode0.mode_name=value>... |
|
For example, to override I2C bus2: |
|
omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 |
|
|
|
oops=panic Always panic on oopses. Default is to just kill the |
|
process, but there is a small probability of |
|
deadlocking the machine. |
|
This will also cause panics on machine check exceptions. |
|
Useful together with panic=30 to trigger a reboot. |
|
|
|
page_alloc.shuffle= |
|
[KNL] Boolean flag to control whether the page allocator |
|
should randomize its free lists. The randomization may |
|
be automatically enabled if the kernel detects it is |
|
running on a platform with a direct-mapped memory-side |
|
cache, and this parameter can be used to |
|
override/disable that behavior. The state of the flag |
|
can be read from sysfs at: |
|
/sys/module/page_alloc/parameters/shuffle. |
|
|
|
page_owner= [KNL] Boot-time page_owner enabling option. |
|
Storage of the information about who allocated |
|
each page is disabled in default. With this switch, |
|
we can turn it on. |
|
on: enable the feature |
|
|
|
page_poison= [KNL] Boot-time parameter changing the state of |
|
poisoning on the buddy allocator, available with |
|
CONFIG_PAGE_POISONING=y. |
|
off: turn off poisoning (default) |
|
on: turn on poisoning |
|
|
|
page_reporting.page_reporting_order= |
|
[KNL] Minimal page reporting order |
|
Format: <integer> |
|
Adjust the minimal page reporting order. The page |
|
reporting is disabled when it exceeds (MAX_ORDER-1). |
|
|
|
panic= [KNL] Kernel behaviour on panic: delay <timeout> |
|
timeout > 0: seconds before rebooting |
|
timeout = 0: wait forever |
|
timeout < 0: reboot immediately |
|
Format: <timeout> |
|
|
|
panic_print= Bitmask for printing system info when panic happens. |
|
User can chose combination of the following bits: |
|
bit 0: print all tasks info |
|
bit 1: print system memory info |
|
bit 2: print timer info |
|
bit 3: print locks info if CONFIG_LOCKDEP is on |
|
bit 4: print ftrace buffer |
|
bit 5: print all printk messages in buffer |
|
|
|
panic_on_taint= Bitmask for conditionally calling panic() in add_taint() |
|
Format: <hex>[,nousertaint] |
|
Hexadecimal bitmask representing the set of TAINT flags |
|
that will cause the kernel to panic when add_taint() is |
|
called with any of the flags in this set. |
|
The optional switch "nousertaint" can be utilized to |
|
prevent userspace forced crashes by writing to sysctl |
|
/proc/sys/kernel/tainted any flagset matching with the |
|
bitmask set on panic_on_taint. |
|
See Documentation/admin-guide/tainted-kernels.rst for |
|
extra details on the taint flags that users can pick |
|
to compose the bitmask to assign to panic_on_taint. |
|
|
|
panic_on_warn panic() instead of WARN(). Useful to cause kdump |
|
on a WARN(). |
|
|
|
crash_kexec_post_notifiers |
|
Run kdump after running panic-notifiers and dumping |
|
kmsg. This only for the users who doubt kdump always |
|
succeeds in any situation. |
|
Note that this also increases risks of kdump failure, |
|
because some panic notifiers can make the crashed |
|
kernel more unstable. |
|
|
|
parkbd.port= [HW] Parallel port number the keyboard adapter is |
|
connected to, default is 0. |
|
Format: <parport#> |
|
parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, |
|
0 for XT, 1 for AT (default is AT). |
|
Format: <mode> |
|
|
|
parport= [HW,PPT] Specify parallel ports. 0 disables. |
|
Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } |
|
Use 'auto' to force the driver to use any |
|
IRQ/DMA settings detected (the default is to |
|
ignore detected IRQ/DMA settings because of |
|
possible conflicts). You can specify the base |
|
address, IRQ, and DMA settings; IRQ and DMA |
|
should be numbers, or 'auto' (for using detected |
|
settings on that particular port), or 'nofifo' |
|
(to avoid using a FIFO even if it is detected). |
|
Parallel ports are assigned in the order they |
|
are specified on the command line, starting |
|
with parport0. |
|
|
|
parport_init_mode= [HW,PPT] |
|
Configure VIA parallel port to operate in |
|
a specific mode. This is necessary on Pegasos |
|
computer where firmware has no options for setting |
|
up parallel port mode and sets it to spp. |
|
Currently this function knows 686a and 8231 chips. |
|
Format: [spp|ps2|epp|ecp|ecpepp] |
|
|
|
pata_legacy.all= [HW,LIBATA] |
|
Format: <int> |
|
Set to non-zero to probe primary and secondary ISA |
|
port ranges on PCI systems where no PCI PATA device |
|
has been found at either range. Disabled by default. |
|
|
|
pata_legacy.autospeed= [HW,LIBATA] |
|
Format: <int> |
|
Set to non-zero if a chip is present that snoops speed |
|
changes. Disabled by default. |
|
|
|
pata_legacy.ht6560a= [HW,LIBATA] |
|
Format: <int> |
|
Set to 1, 2, or 3 for HT 6560A on the primary channel, |
|
the secondary channel, or both channels respectively. |
|
Disabled by default. |
|
|
|
pata_legacy.ht6560b= [HW,LIBATA] |
|
Format: <int> |
|
Set to 1, 2, or 3 for HT 6560B on the primary channel, |
|
the secondary channel, or both channels respectively. |
|
Disabled by default. |
|
|
|
pata_legacy.iordy_mask= [HW,LIBATA] |
|
Format: <int> |
|
IORDY enable mask. Set individual bits to allow IORDY |
|
for the respective channel. Bit 0 is for the first |
|
legacy channel handled by this driver, bit 1 is for |
|
the second channel, and so on. The sequence will often |
|
correspond to the primary legacy channel, the secondary |
|
legacy channel, and so on, but the handling of a PCI |
|
bus and the use of other driver options may interfere |
|
with the sequence. By default IORDY is allowed across |
|
all channels. |
|
|
|
pata_legacy.opti82c46x= [HW,LIBATA] |
|
Format: <int> |
|
Set to 1, 2, or 3 for Opti 82c611A on the primary |
|
channel, the secondary channel, or both channels |
|
respectively. Disabled by default. |
|
|
|
pata_legacy.opti82c611a= [HW,LIBATA] |
|
Format: <int> |
|
Set to 1, 2, or 3 for Opti 82c465MV on the primary |
|
channel, the secondary channel, or both channels |
|
respectively. Disabled by default. |
|
|
|
pata_legacy.pio_mask= [HW,LIBATA] |
|
Format: <int> |
|
PIO mode mask for autospeed devices. Set individual |
|
bits to allow the use of the respective PIO modes. |
|
Bit 0 is for mode 0, bit 1 is for mode 1, and so on. |
|
All modes allowed by default. |
|
|
|
pata_legacy.probe_all= [HW,LIBATA] |
|
Format: <int> |
|
Set to non-zero to probe tertiary and further ISA |
|
port ranges on PCI systems. Disabled by default. |
|
|
|
pata_legacy.probe_mask= [HW,LIBATA] |
|
Format: <int> |
|
Probe mask for legacy ISA PATA ports. Depending on |
|
platform configuration and the use of other driver |
|
options up to 6 legacy ports are supported: 0x1f0, |
|
0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing |
|
of individual ports can be disabled by setting the |
|
corresponding bits in the mask to 1. Bit 0 is for |
|
the first port in the list above (0x1f0), and so on. |
|
By default all supported ports are probed. |
|
|
|
pata_legacy.qdi= [HW,LIBATA] |
|
Format: <int> |
|
Set to non-zero to probe QDI controllers. By default |
|
set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise. |
|
|
|
pata_legacy.winbond= [HW,LIBATA] |
|
Format: <int> |
|
Set to non-zero to probe Winbond controllers. Use |
|
the standard I/O port (0x130) if 1, otherwise the |
|
value given is the I/O port to use (typically 0x1b0). |
|
By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE, |
|
0 otherwise. |
|
|
|
pata_platform.pio_mask= [HW,LIBATA] |
|
Format: <int> |
|
Supported PIO mode mask. Set individual bits to allow |
|
the use of the respective PIO modes. Bit 0 is for |
|
mode 0, bit 1 is for mode 1, and so on. Mode 0 only |
|
allowed by default. |
|
|
|
pause_on_oops= |
|
Halt all CPUs after the first oops has been printed for |
|
the specified number of seconds. This is to be used if |
|
your oopses keep scrolling off the screen. |
|
|
|
pcbit= [HW,ISDN] |
|
|
|
pcd. [PARIDE] |
|
See header of drivers/block/paride/pcd.c. |
|
See also Documentation/admin-guide/blockdev/paride.rst. |
|
|
|
pci=option[,option...] [PCI] various PCI subsystem options. |
|
|
|
Some options herein operate on a specific device |
|
or a set of devices (<pci_dev>). These are |
|
specified in one of the following formats: |
|
|
|
[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* |
|
pci:<vendor>:<device>[:<subvendor>:<subdevice>] |
|
|
|
Note: the first format specifies a PCI |
|
bus/device/function address which may change |
|
if new hardware is inserted, if motherboard |
|
firmware changes, or due to changes caused |
|
by other kernel parameters. If the |
|
domain is left unspecified, it is |
|
taken to be zero. Optionally, a path |
|
to a device through multiple device/function |
|
addresses can be specified after the base |
|
address (this is more robust against |
|
renumbering issues). The second format |
|
selects devices using IDs from the |
|
configuration space which may match multiple |
|
devices in the system. |
|
|
|
earlydump dump PCI config space before the kernel |
|
changes anything |
|
off [X86] don't probe for the PCI bus |
|
bios [X86-32] force use of PCI BIOS, don't access |
|
the hardware directly. Use this if your machine |
|
has a non-standard PCI host bridge. |
|
nobios [X86-32] disallow use of PCI BIOS, only direct |
|
hardware access methods are allowed. Use this |
|
if you experience crashes upon bootup and you |
|
suspect they are caused by the BIOS. |
|
conf1 [X86] Force use of PCI Configuration Access |
|
Mechanism 1 (config address in IO port 0xCF8, |
|
data in IO port 0xCFC, both 32-bit). |
|
conf2 [X86] Force use of PCI Configuration Access |
|
Mechanism 2 (IO port 0xCF8 is an 8-bit port for |
|
the function, IO port 0xCFA, also 8-bit, sets |
|
bus number. The config space is then accessed |
|
through ports 0xC000-0xCFFF). |
|
See http://wiki.osdev.org/PCI for more info |
|
on the configuration access mechanisms. |
|
noaer [PCIE] If the PCIEAER kernel config parameter is |
|
enabled, this kernel boot option can be used to |
|
disable the use of PCIE advanced error reporting. |
|
nodomains [PCI] Disable support for multiple PCI |
|
root domains (aka PCI segments, in ACPI-speak). |
|
nommconf [X86] Disable use of MMCONFIG for PCI |
|
Configuration |
|
check_enable_amd_mmconf [X86] check for and enable |
|
properly configured MMIO access to PCI |
|
config space on AMD family 10h CPU |
|
nomsi [MSI] If the PCI_MSI kernel config parameter is |
|
enabled, this kernel boot option can be used to |
|
disable the use of MSI interrupts system-wide. |
|
noioapicquirk [APIC] Disable all boot interrupt quirks. |
|
Safety option to keep boot IRQs enabled. This |
|
should never be necessary. |
|
ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
|
primary IO-APIC for bridges that cannot disable |
|
boot IRQs. This fixes a source of spurious IRQs |
|
when the system masks IRQs. |
|
noioapicreroute [APIC] Disable workaround that uses the |
|
boot IRQ equivalent of an IRQ that connects to |
|
a chipset where boot IRQs cannot be disabled. |
|
The opposite of ioapicreroute. |
|
biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
|
routing table. These calls are known to be buggy |
|
on several machines and they hang the machine |
|
when used, but on other computers it's the only |
|
way to get the interrupt routing table. Try |
|
this option if the kernel is unable to allocate |
|
IRQs or discover secondary PCI buses on your |
|
motherboard. |
|
rom [X86] Assign address space to expansion ROMs. |
|
Use with caution as certain devices share |
|
address decoders between ROMs and other |
|
resources. |
|
norom [X86] Do not assign address space to |
|
expansion ROMs that do not already have |
|
BIOS assigned address ranges. |
|
nobar [X86] Do not assign address space to the |
|
BARs that weren't assigned by the BIOS. |
|
irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
|
assigned automatically to PCI devices. You can |
|
make the kernel exclude IRQs of your ISA cards |
|
this way. |
|
pirqaddr=0xAAAAA [X86] Specify the physical address |
|
of the PIRQ table (normally generated |
|
by the BIOS) if it is outside the |
|
F0000h-100000h range. |
|
lastbus=N [X86] Scan all buses thru bus #N. Can be |
|
useful if the kernel is unable to find your |
|
secondary buses and you want to tell it |
|
explicitly which ones they are. |
|
assign-busses [X86] Always assign all PCI bus |
|
numbers ourselves, overriding |
|
whatever the firmware may have done. |
|
usepirqmask [X86] Honor the possible IRQ mask stored |
|
in the BIOS $PIR table. This is needed on |
|
some systems with broken BIOSes, notably |
|
some HP Pavilion N5400 and Omnibook XE3 |
|
notebooks. This will have no effect if ACPI |
|
IRQ routing is enabled. |
|
noacpi [X86] Do not use ACPI for IRQ routing |
|
or for PCI scanning. |
|
use_crs [X86] Use PCI host bridge window information |
|
from ACPI. On BIOSes from 2008 or later, this |
|
is enabled by default. If you need to use this, |
|
please report a bug. |
|
nocrs [X86] Ignore PCI host bridge windows from ACPI. |
|
If you need to use this, please report a bug. |
|
routeirq Do IRQ routing for all PCI devices. |
|
This is normally done in pci_enable_device(), |
|
so this option is a temporary workaround |
|
for broken drivers that don't call it. |
|
skip_isa_align [X86] do not align io start addr, so can |
|
handle more pci cards |
|
noearly [X86] Don't do any early type 1 scanning. |
|
This might help on some broken boards which |
|
machine check when some devices' config space |
|
is read. But various workarounds are disabled |
|
and some IOMMU drivers will not work. |
|
bfsort Sort PCI devices into breadth-first order. |
|
This sorting is done to get a device |
|
order compatible with older (<= 2.4) kernels. |
|
nobfsort Don't sort PCI devices into breadth-first order. |
|
pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) |
|
tuning and use the BIOS-configured MPS defaults. |
|
pcie_bus_safe Set every device's MPS to the largest value |
|
supported by all devices below the root complex. |
|
pcie_bus_perf Set device MPS to the largest allowable MPS |
|
based on its parent bus. Also set MRRS (Max |
|
Read Request Size) to the largest supported |
|
value (no larger than the MPS that the device |
|
or bus can support) for best performance. |
|
pcie_bus_peer2peer Set every device's MPS to 128B, which |
|
every device is guaranteed to support. This |
|
configuration allows peer-to-peer DMA between |
|
any pair of devices, possibly at the cost of |
|
reduced performance. This also guarantees |
|
that hot-added devices will work. |
|
cbiosize=nn[KMG] The fixed amount of bus space which is |
|
reserved for the CardBus bridge's IO window. |
|
The default value is 256 bytes. |
|
cbmemsize=nn[KMG] The fixed amount of bus space which is |
|
reserved for the CardBus bridge's memory |
|
window. The default value is 64 megabytes. |
|
resource_alignment= |
|
Format: |
|
[<order of align>@]<pci_dev>[; ...] |
|
Specifies alignment and device to reassign |
|
aligned memory resources. How to |
|
specify the device is described above. |
|
If <order of align> is not specified, |
|
PAGE_SIZE is used as alignment. |
|
A PCI-PCI bridge can be specified if resource |
|
windows need to be expanded. |
|
To specify the alignment for several |
|
instances of a device, the PCI vendor, |
|
device, subvendor, and subdevice may be |
|
specified, e.g., 12@pci:8086:9c22:103c:198f |
|
for 4096-byte alignment. |
|
ecrc= Enable/disable PCIe ECRC (transaction layer |
|
end-to-end CRC checking). |
|
bios: Use BIOS/firmware settings. This is the |
|
the default. |
|
off: Turn ECRC off |
|
on: Turn ECRC on. |
|
hpiosize=nn[KMG] The fixed amount of bus space which is |
|
reserved for hotplug bridge's IO window. |
|
Default size is 256 bytes. |
|
hpmmiosize=nn[KMG] The fixed amount of bus space which is |
|
reserved for hotplug bridge's MMIO window. |
|
Default size is 2 megabytes. |
|
hpmmioprefsize=nn[KMG] The fixed amount of bus space which is |
|
reserved for hotplug bridge's MMIO_PREF window. |
|
Default size is 2 megabytes. |
|
hpmemsize=nn[KMG] The fixed amount of bus space which is |
|
reserved for hotplug bridge's MMIO and |
|
MMIO_PREF window. |
|
Default size is 2 megabytes. |
|
hpbussize=nn The minimum amount of additional bus numbers |
|
reserved for buses below a hotplug bridge. |
|
Default is 1. |
|
realloc= Enable/disable reallocating PCI bridge resources |
|
if allocations done by BIOS are too small to |
|
accommodate resources required by all child |
|
devices. |
|
off: Turn realloc off |
|
on: Turn realloc on |
|
realloc same as realloc=on |
|
noari do not use PCIe ARI. |
|
noats [PCIE, Intel-IOMMU, AMD-IOMMU] |
|
do not use PCIe ATS (and IOMMU device IOTLB). |
|
pcie_scan_all Scan all possible PCIe devices. Otherwise we |
|
only look for one device below a PCIe downstream |
|
port. |
|
big_root_window Try to add a big 64bit memory window to the PCIe |
|
root complex on AMD CPUs. Some GFX hardware |
|
can resize a BAR to allow access to all VRAM. |
|
Adding the window is slightly risky (it may |
|
conflict with unreported devices), so this |
|
taints the kernel. |
|
disable_acs_redir=<pci_dev>[; ...] |
|
Specify one or more PCI devices (in the format |
|
specified above) separated by semicolons. |
|
Each device specified will have the PCI ACS |
|
redirect capabilities forced off which will |
|
allow P2P traffic between devices through |
|
bridges without forcing it upstream. Note: |
|
this removes isolation between devices and |
|
may put more devices in an IOMMU group. |
|
force_floating [S390] Force usage of floating interrupts. |
|
nomio [S390] Do not use MIO instructions. |
|
norid [S390] ignore the RID field and force use of |
|
one PCI domain per PCI function |
|
|
|
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
|
Management. |
|
off Disable ASPM. |
|
force Enable ASPM even on devices that claim not to support it. |
|
WARNING: Forcing ASPM on may cause system lockups. |
|
|
|
pcie_ports= [PCIE] PCIe port services handling: |
|
native Use native PCIe services (PME, AER, DPC, PCIe hotplug) |
|
even if the platform doesn't give the OS permission to |
|
use them. This may cause conflicts if the platform |
|
also tries to use these services. |
|
dpc-native Use native PCIe service for DPC only. May |
|
cause conflicts if firmware uses AER or DPC. |
|
compat Disable native PCIe services (PME, AER, DPC, PCIe |
|
hotplug). |
|
|
|
pcie_port_pm= [PCIE] PCIe port power management handling: |
|
off Disable power management of all PCIe ports |
|
force Forcibly enable power management of all PCIe ports |
|
|
|
pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
|
nomsi Do not use MSI for native PCIe PME signaling (this makes |
|
all PCIe root ports use INTx for all services). |
|
|
|
pcmv= [HW,PCMCIA] BadgePAD 4 |
|
|
|
pd_ignore_unused |
|
[PM] |
|
Keep all power-domains already enabled by bootloader on, |
|
even if no driver has claimed them. This is useful |
|
for debug and development, but should not be |
|
needed on a platform with proper driver support. |
|
|
|
pd. [PARIDE] |
|
See Documentation/admin-guide/blockdev/paride.rst. |
|
|
|
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at |
|
boot time. |
|
Format: { 0 | 1 } |
|
See arch/parisc/kernel/pdc_chassis.c |
|
|
|
percpu_alloc= Select which percpu first chunk allocator to use. |
|
Currently supported values are "embed" and "page". |
|
Archs may support subset or none of the selections. |
|
See comments in mm/percpu.c for details on each |
|
allocator. This parameter is primarily for debugging |
|
and performance comparison. |
|
|
|
pf. [PARIDE] |
|
See Documentation/admin-guide/blockdev/paride.rst. |
|
|
|
pg. [PARIDE] |
|
See Documentation/admin-guide/blockdev/paride.rst. |
|
|
|
pirq= [SMP,APIC] Manual mp-table setup |
|
See Documentation/x86/i386/IO-APIC.rst. |
|
|
|
plip= [PPT,NET] Parallel port network link |
|
Format: { parport<nr> | timid | 0 } |
|
See also Documentation/admin-guide/parport.rst. |
|
|
|
pmtmr= [X86] Manual setup of pmtmr I/O Port. |
|
Override pmtimer IOPort with a hex value. |
|
e.g. pmtmr=0x508 |
|
|
|
pm_debug_messages [SUSPEND,KNL] |
|
Enable suspend/resume debug messages during boot up. |
|
|
|
pnp.debug=1 [PNP] |
|
Enable PNP debug messages (depends on the |
|
CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time |
|
via /sys/module/pnp/parameters/debug. We always show |
|
current resource usage; turning this on also shows |
|
possible settings and some assignment information. |
|
|
|
pnpacpi= [ACPI] |
|
{ off } |
|
|
|
pnpbios= [ISAPNP] |
|
{ on | off | curr | res | no-curr | no-res } |
|
|
|
pnp_reserve_irq= |
|
[ISAPNP] Exclude IRQs for the autoconfiguration |
|
|
|
pnp_reserve_dma= |
|
[ISAPNP] Exclude DMAs for the autoconfiguration |
|
|
|
pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration |
|
Ranges are in pairs (I/O port base and size). |
|
|
|
pnp_reserve_mem= |
|
[ISAPNP] Exclude memory regions for the |
|
autoconfiguration. |
|
Ranges are in pairs (memory base and size). |
|
|
|
ports= [IP_VS_FTP] IPVS ftp helper module |
|
Default is 21. |
|
Up to 8 (IP_VS_APP_MAX_PORTS) ports |
|
may be specified. |
|
Format: <port>,<port>.... |
|
|
|
powersave=off [PPC] This option disables power saving features. |
|
It specifically disables cpuidle and sets the |
|
platform machine description specific power_save |
|
function to NULL. On Idle the CPU just reduces |
|
execution priority. |
|
|
|
ppc_strict_facility_enable |
|
[PPC] This option catches any kernel floating point, |
|
Altivec, VSX and SPE outside of regions specifically |
|
allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). |
|
There is some performance impact when enabling this. |
|
|
|
ppc_tm= [PPC] |
|
Format: {"off"} |
|
Disable Hardware Transactional Memory |
|
|
|
preempt= [KNL] |
|
Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC |
|
none - Limited to cond_resched() calls |
|
voluntary - Limited to cond_resched() and might_sleep() calls |
|
full - Any section that isn't explicitly preempt disabled |
|
can be preempted anytime. |
|
|
|
print-fatal-signals= |
|
[KNL] debug: print fatal signals |
|
|
|
If enabled, warn about various signal handling |
|
related application anomalies: too many signals, |
|
too many POSIX.1 timers, fatal signals causing a |
|
coredump - etc. |
|
|
|
If you hit the warning due to signal overflow, |
|
you might want to try "ulimit -i unlimited". |
|
|
|
default: off. |
|
|
|
printk.always_kmsg_dump= |
|
Trigger kmsg_dump for cases other than kernel oops or |
|
panics |
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable) |
|
default: disabled |
|
|
|
printk.console_no_auto_verbose= |
|
Disable console loglevel raise on oops, panic |
|
or lockdep-detected issues (only if lock debug is on). |
|
With an exception to setups with low baudrate on |
|
serial console, keeping this 0 is a good choice |
|
in order to provide more debug information. |
|
Format: <bool> |
|
default: 0 (auto_verbose is enabled) |
|
|
|
printk.devkmsg={on,off,ratelimit} |
|
Control writing to /dev/kmsg. |
|
on - unlimited logging to /dev/kmsg from userspace |
|
off - logging to /dev/kmsg disabled |
|
ratelimit - ratelimit the logging |
|
Default: ratelimit |
|
|
|
printk.time= Show timing data prefixed to each printk message line |
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable) |
|
|
|
processor.max_cstate= [HW,ACPI] |
|
Limit processor to maximum C-state |
|
max_cstate=9 overrides any DMI blacklist limit. |
|
|
|
processor.nocst [HW,ACPI] |
|
Ignore the _CST method to determine C-states, |
|
instead using the legacy FADT method |
|
|
|
profile= [KNL] Enable kernel profiling via /proc/profile |
|
Format: [<profiletype>,]<number> |
|
Param: <profiletype>: "schedule", "sleep", or "kvm" |
|
[defaults to kernel profiling] |
|
Param: "schedule" - profile schedule points. |
|
Param: "sleep" - profile D-state sleeping (millisecs). |
|
Requires CONFIG_SCHEDSTATS |
|
Param: "kvm" - profile VM exits. |
|
Param: <number> - step/bucket size as a power of 2 for |
|
statistical time based profiling. |
|
|
|
prompt_ramdisk= [RAM] [Deprecated] |
|
|
|
prot_virt= [S390] enable hosting protected virtual machines |
|
isolated from the hypervisor (if hardware supports |
|
that). |
|
Format: <bool> |
|
|
|
psi= [KNL] Enable or disable pressure stall information |
|
tracking. |
|
Format: <bool> |
|
|
|
psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
|
probe for; one of (bare|imps|exps|lifebook|any). |
|
psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
|
per second. |
|
psmouse.resetafter= [HW,MOUSE] |
|
Try to reset the device after so many bad packets |
|
(0 = never). |
|
psmouse.resolution= |
|
[HW,MOUSE] Set desired mouse resolution, in dpi. |
|
psmouse.smartscroll= |
|
[HW,MOUSE] Controls Logitech smartscroll autorepeat. |
|
0 = disabled, 1 = enabled (default). |
|
|
|
pstore.backend= Specify the name of the pstore backend to use |
|
|
|
pt. [PARIDE] |
|
See Documentation/admin-guide/blockdev/paride.rst. |
|
|
|
pti= [X86-64] Control Page Table Isolation of user and |
|
kernel address spaces. Disabling this feature |
|
removes hardening, but improves performance of |
|
system calls and interrupts. |
|
|
|
on - unconditionally enable |
|
off - unconditionally disable |
|
auto - kernel detects whether your CPU model is |
|
vulnerable to issues that PTI mitigates |
|
|
|
Not specifying this option is equivalent to pti=auto. |
|
|
|
nopti [X86-64] |
|
Equivalent to pti=off |
|
|
|
pty.legacy_count= |
|
[KNL] Number of legacy pty's. Overwrites compiled-in |
|
default number. |
|
|
|
quiet [KNL] Disable most log messages |
|
|
|
r128= [HW,DRM] |
|
|
|
raid= [HW,RAID] |
|
See Documentation/admin-guide/md.rst. |
|
|
|
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
|
See Documentation/admin-guide/blockdev/ramdisk.rst. |
|
|
|
ramdisk_start= [RAM] RAM disk image start address |
|
|
|
random.trust_cpu={on,off} |
|
[KNL] Enable or disable trusting the use of the |
|
CPU's random number generator (if available) to |
|
fully seed the kernel's CRNG. Default is controlled |
|
by CONFIG_RANDOM_TRUST_CPU. |
|
|
|
randomize_kstack_offset= |
|
[KNL] Enable or disable kernel stack offset |
|
randomization, which provides roughly 5 bits of |
|
entropy, frustrating memory corruption attacks |
|
that depend on stack address determinism or |
|
cross-syscall address exposures. This is only |
|
available on architectures that have defined |
|
CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET. |
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable) |
|
Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT. |
|
|
|
ras=option[,option,...] [KNL] RAS-specific options |
|
|
|
cec_disable [X86] |
|
Disable the Correctable Errors Collector, |
|
see CONFIG_RAS_CEC help text. |
|
|
|
rcu_nocbs= [KNL] |
|
The argument is a cpu list, as described above. |
|
|
|
In kernels built with CONFIG_RCU_NOCB_CPU=y, set |
|
the specified list of CPUs to be no-callback CPUs. |
|
Invocation of these CPUs' RCU callbacks will be |
|
offloaded to "rcuox/N" kthreads created for that |
|
purpose, where "x" is "p" for RCU-preempt, and |
|
"s" for RCU-sched, and "N" is the CPU number. |
|
This reduces OS jitter on the offloaded CPUs, |
|
which can be useful for HPC and real-time |
|
workloads. It can also improve energy efficiency |
|
for asymmetric multiprocessors. |
|
|
|
rcu_nocb_poll [KNL] |
|
Rather than requiring that offloaded CPUs |
|
(specified by rcu_nocbs= above) explicitly |
|
awaken the corresponding "rcuoN" kthreads, |
|
make these kthreads poll for callbacks. |
|
This improves the real-time response for the |
|
offloaded CPUs by relieving them of the need to |
|
wake up the corresponding kthread, but degrades |
|
energy efficiency by requiring that the kthreads |
|
periodically wake up to do the polling. |
|
|
|
rcutree.blimit= [KNL] |
|
Set maximum number of finished RCU callbacks to |
|
process in one batch. |
|
|
|
rcutree.dump_tree= [KNL] |
|
Dump the structure of the rcu_node combining tree |
|
out at early boot. This is used for diagnostic |
|
purposes, to verify correct tree setup. |
|
|
|
rcutree.gp_cleanup_delay= [KNL] |
|
Set the number of jiffies to delay each step of |
|
RCU grace-period cleanup. |
|
|
|
rcutree.gp_init_delay= [KNL] |
|
Set the number of jiffies to delay each step of |
|
RCU grace-period initialization. |
|
|
|
rcutree.gp_preinit_delay= [KNL] |
|
Set the number of jiffies to delay each step of |
|
RCU grace-period pre-initialization, that is, |
|
the propagation of recent CPU-hotplug changes up |
|
the rcu_node combining tree. |
|
|
|
rcutree.use_softirq= [KNL] |
|
If set to zero, move all RCU_SOFTIRQ processing to |
|
per-CPU rcuc kthreads. Defaults to a non-zero |
|
value, meaning that RCU_SOFTIRQ is used by default. |
|
Specify rcutree.use_softirq=0 to use rcuc kthreads. |
|
|
|
But note that CONFIG_PREEMPT_RT=y kernels disable |
|
this kernel boot parameter, forcibly setting it |
|
to zero. |
|
|
|
rcutree.rcu_fanout_exact= [KNL] |
|
Disable autobalancing of the rcu_node combining |
|
tree. This is used by rcutorture, and might |
|
possibly be useful for architectures having high |
|
cache-to-cache transfer latencies. |
|
|
|
rcutree.rcu_fanout_leaf= [KNL] |
|
Change the number of CPUs assigned to each |
|
leaf rcu_node structure. Useful for very |
|
large systems, which will choose the value 64, |
|
and for NUMA systems with large remote-access |
|
latencies, which will choose a value aligned |
|
with the appropriate hardware boundaries. |
|
|
|
rcutree.rcu_min_cached_objs= [KNL] |
|
Minimum number of objects which are cached and |
|
maintained per one CPU. Object size is equal |
|
to PAGE_SIZE. The cache allows to reduce the |
|
pressure to page allocator, also it makes the |
|
whole algorithm to behave better in low memory |
|
condition. |
|
|
|
rcutree.rcu_delay_page_cache_fill_msec= [KNL] |
|
Set the page-cache refill delay (in milliseconds) |
|
in response to low-memory conditions. The range |
|
of permitted values is in the range 0:100000. |
|
|
|
rcutree.jiffies_till_first_fqs= [KNL] |
|
Set delay from grace-period initialization to |
|
first attempt to force quiescent states. |
|
Units are jiffies, minimum value is zero, |
|
and maximum value is HZ. |
|
|
|
rcutree.jiffies_till_next_fqs= [KNL] |
|
Set delay between subsequent attempts to force |
|
quiescent states. Units are jiffies, minimum |
|
value is one, and maximum value is HZ. |
|
|
|
rcutree.jiffies_till_sched_qs= [KNL] |
|
Set required age in jiffies for a |
|
given grace period before RCU starts |
|
soliciting quiescent-state help from |
|
rcu_note_context_switch() and cond_resched(). |
|
If not specified, the kernel will calculate |
|
a value based on the most recent settings |
|
of rcutree.jiffies_till_first_fqs |
|
and rcutree.jiffies_till_next_fqs. |
|
This calculated value may be viewed in |
|
rcutree.jiffies_to_sched_qs. Any attempt to set |
|
rcutree.jiffies_to_sched_qs will be cheerfully |
|
overwritten. |
|
|
|
rcutree.kthread_prio= [KNL,BOOT] |
|
Set the SCHED_FIFO priority of the RCU per-CPU |
|
kthreads (rcuc/N). This value is also used for |
|
the priority of the RCU boost threads (rcub/N) |
|
and for the RCU grace-period kthreads (rcu_bh, |
|
rcu_preempt, and rcu_sched). If RCU_BOOST is |
|
set, valid values are 1-99 and the default is 1 |
|
(the least-favored priority). Otherwise, when |
|
RCU_BOOST is not set, valid values are 0-99 and |
|
the default is zero (non-realtime operation). |
|
|
|
rcutree.rcu_nocb_gp_stride= [KNL] |
|
Set the number of NOCB callback kthreads in |
|
each group, which defaults to the square root |
|
of the number of CPUs. Larger numbers reduce |
|
the wakeup overhead on the global grace-period |
|
kthread, but increases that same overhead on |
|
each group's NOCB grace-period kthread. |
|
|
|
rcutree.qhimark= [KNL] |
|
Set threshold of queued RCU callbacks beyond which |
|
batch limiting is disabled. |
|
|
|
rcutree.qlowmark= [KNL] |
|
Set threshold of queued RCU callbacks below which |
|
batch limiting is re-enabled. |
|
|
|
rcutree.qovld= [KNL] |
|
Set threshold of queued RCU callbacks beyond which |
|
RCU's force-quiescent-state scan will aggressively |
|
enlist help from cond_resched() and sched IPIs to |
|
help CPUs more quickly reach quiescent states. |
|
Set to less than zero to make this be set based |
|
on rcutree.qhimark at boot time and to zero to |
|
disable more aggressive help enlistment. |
|
|
|
rcutree.rcu_idle_gp_delay= [KNL] |
|
Set wakeup interval for idle CPUs that have |
|
RCU callbacks (RCU_FAST_NO_HZ=y). |
|
|
|
rcutree.rcu_kick_kthreads= [KNL] |
|
Cause the grace-period kthread to get an extra |
|
wake_up() if it sleeps three times longer than |
|
it should at force-quiescent-state time. |
|
This wake_up() will be accompanied by a |
|
WARN_ONCE() splat and an ftrace_dump(). |
|
|
|
rcutree.rcu_unlock_delay= [KNL] |
|
In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, |
|
this specifies an rcu_read_unlock()-time delay |
|
in microseconds. This defaults to zero. |
|
Larger delays increase the probability of |
|
catching RCU pointer leaks, that is, buggy use |
|
of RCU-protected pointers after the relevant |
|
rcu_read_unlock() has completed. |
|
|
|
rcutree.sysrq_rcu= [KNL] |
|
Commandeer a sysrq key to dump out Tree RCU's |
|
rcu_node tree with an eye towards determining |
|
why a new grace period has not yet started. |
|
|
|
rcuscale.gp_async= [KNL] |
|
Measure performance of asynchronous |
|
grace-period primitives such as call_rcu(). |
|
|
|
rcuscale.gp_async_max= [KNL] |
|
Specify the maximum number of outstanding |
|
callbacks per writer thread. When a writer |
|
thread exceeds this limit, it invokes the |
|
corresponding flavor of rcu_barrier() to allow |
|
previously posted callbacks to drain. |
|
|
|
rcuscale.gp_exp= [KNL] |
|
Measure performance of expedited synchronous |
|
grace-period primitives. |
|
|
|
rcuscale.holdoff= [KNL] |
|
Set test-start holdoff period. The purpose of |
|
this parameter is to delay the start of the |
|
test until boot completes in order to avoid |
|
interference. |
|
|
|
rcuscale.kfree_rcu_test= [KNL] |
|
Set to measure performance of kfree_rcu() flooding. |
|
|
|
rcuscale.kfree_rcu_test_double= [KNL] |
|
Test the double-argument variant of kfree_rcu(). |
|
If this parameter has the same value as |
|
rcuscale.kfree_rcu_test_single, both the single- |
|
and double-argument variants are tested. |
|
|
|
rcuscale.kfree_rcu_test_single= [KNL] |
|
Test the single-argument variant of kfree_rcu(). |
|
If this parameter has the same value as |
|
rcuscale.kfree_rcu_test_double, both the single- |
|
and double-argument variants are tested. |
|
|
|
rcuscale.kfree_nthreads= [KNL] |
|
The number of threads running loops of kfree_rcu(). |
|
|
|
rcuscale.kfree_alloc_num= [KNL] |
|
Number of allocations and frees done in an iteration. |
|
|
|
rcuscale.kfree_loops= [KNL] |
|
Number of loops doing rcuscale.kfree_alloc_num number |
|
of allocations and frees. |
|
|
|
rcuscale.nreaders= [KNL] |
|
Set number of RCU readers. The value -1 selects |
|
N, where N is the number of CPUs. A value |
|
"n" less than -1 selects N-n+1, where N is again |
|
the number of CPUs. For example, -2 selects N |
|
(the number of CPUs), -3 selects N+1, and so on. |
|
A value of "n" less than or equal to -N selects |
|
a single reader. |
|
|
|
rcuscale.nwriters= [KNL] |
|
Set number of RCU writers. The values operate |
|
the same as for rcuscale.nreaders. |
|
N, where N is the number of CPUs |
|
|
|
rcuscale.perf_type= [KNL] |
|
Specify the RCU implementation to test. |
|
|
|
rcuscale.shutdown= [KNL] |
|
Shut the system down after performance tests |
|
complete. This is useful for hands-off automated |
|
testing. |
|
|
|
rcuscale.verbose= [KNL] |
|
Enable additional printk() statements. |
|
|
|
rcuscale.writer_holdoff= [KNL] |
|
Write-side holdoff between grace periods, |
|
in microseconds. The default of zero says |
|
no holdoff. |
|
|
|
rcutorture.fqs_duration= [KNL] |
|
Set duration of force_quiescent_state bursts |
|
in microseconds. |
|
|
|
rcutorture.fqs_holdoff= [KNL] |
|
Set holdoff time within force_quiescent_state bursts |
|
in microseconds. |
|
|
|
rcutorture.fqs_stutter= [KNL] |
|
Set wait time between force_quiescent_state bursts |
|
in seconds. |
|
|
|
rcutorture.fwd_progress= [KNL] |
|
Enable RCU grace-period forward-progress testing |
|
for the types of RCU supporting this notion. |
|
|
|
rcutorture.fwd_progress_div= [KNL] |
|
Specify the fraction of a CPU-stall-warning |
|
period to do tight-loop forward-progress testing. |
|
|
|
rcutorture.fwd_progress_holdoff= [KNL] |
|
Number of seconds to wait between successive |
|
forward-progress tests. |
|
|
|
rcutorture.fwd_progress_need_resched= [KNL] |
|
Enclose cond_resched() calls within checks for |
|
need_resched() during tight-loop forward-progress |
|
testing. |
|
|
|
rcutorture.gp_cond= [KNL] |
|
Use conditional/asynchronous update-side |
|
primitives, if available. |
|
|
|
rcutorture.gp_exp= [KNL] |
|
Use expedited update-side primitives, if available. |
|
|
|
rcutorture.gp_normal= [KNL] |
|
Use normal (non-expedited) asynchronous |
|
update-side primitives, if available. |
|
|
|
rcutorture.gp_sync= [KNL] |
|
Use normal (non-expedited) synchronous |
|
update-side primitives, if available. If all |
|
of rcutorture.gp_cond=, rcutorture.gp_exp=, |
|
rcutorture.gp_normal=, and rcutorture.gp_sync= |
|
are zero, rcutorture acts as if is interpreted |
|
they are all non-zero. |
|
|
|
rcutorture.irqreader= [KNL] |
|
Run RCU readers from irq handlers, or, more |
|
accurately, from a timer handler. Not all RCU |
|
flavors take kindly to this sort of thing. |
|
|
|
rcutorture.leakpointer= [KNL] |
|
Leak an RCU-protected pointer out of the reader. |
|
This can of course result in splats, and is |
|
intended to test the ability of things like |
|
CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect |
|
such leaks. |
|
|
|
rcutorture.n_barrier_cbs= [KNL] |
|
Set callbacks/threads for rcu_barrier() testing. |
|
|
|
rcutorture.nfakewriters= [KNL] |
|
Set number of concurrent RCU writers. These just |
|
stress RCU, they don't participate in the actual |
|
test, hence the "fake". |
|
|
|
rcutorture.nocbs_nthreads= [KNL] |
|
Set number of RCU callback-offload togglers. |
|
Zero (the default) disables toggling. |
|
|
|
rcutorture.nocbs_toggle= [KNL] |
|
Set the delay in milliseconds between successive |
|
callback-offload toggling attempts. |
|
|
|
rcutorture.nreaders= [KNL] |
|
Set number of RCU readers. The value -1 selects |
|
N-1, where N is the number of CPUs. A value |
|
"n" less than -1 selects N-n-2, where N is again |
|
the number of CPUs. For example, -2 selects N |
|
(the number of CPUs), -3 selects N+1, and so on. |
|
|
|
rcutorture.object_debug= [KNL] |
|
Enable debug-object double-call_rcu() testing. |
|
|
|
rcutorture.onoff_holdoff= [KNL] |
|
Set time (s) after boot for CPU-hotplug testing. |
|
|
|
rcutorture.onoff_interval= [KNL] |
|
Set time (jiffies) between CPU-hotplug operations, |
|
or zero to disable CPU-hotplug testing. |
|
|
|
rcutorture.read_exit= [KNL] |
|
Set the number of read-then-exit kthreads used |
|
to test the interaction of RCU updaters and |
|
task-exit processing. |
|
|
|
rcutorture.read_exit_burst= [KNL] |
|
The number of times in a given read-then-exit |
|
episode that a set of read-then-exit kthreads |
|
is spawned. |
|
|
|
rcutorture.read_exit_delay= [KNL] |
|
The delay, in seconds, between successive |
|
read-then-exit testing episodes. |
|
|
|
rcutorture.shuffle_interval= [KNL] |
|
Set task-shuffle interval (s). Shuffling tasks |
|
allows some CPUs to go into dyntick-idle mode |
|
during the rcutorture test. |
|
|
|
rcutorture.shutdown_secs= [KNL] |
|
Set time (s) after boot system shutdown. This |
|
is useful for hands-off automated testing. |
|
|
|
rcutorture.stall_cpu= [KNL] |
|
Duration of CPU stall (s) to test RCU CPU stall |
|
warnings, zero to disable. |
|
|
|
rcutorture.stall_cpu_block= [KNL] |
|
Sleep while stalling if set. This will result |
|
in warnings from preemptible RCU in addition |
|
to any other stall-related activity. |
|
|
|
rcutorture.stall_cpu_holdoff= [KNL] |
|
Time to wait (s) after boot before inducing stall. |
|
|
|
rcutorture.stall_cpu_irqsoff= [KNL] |
|
Disable interrupts while stalling if set. |
|
|
|
rcutorture.stall_gp_kthread= [KNL] |
|
Duration (s) of forced sleep within RCU |
|
grace-period kthread to test RCU CPU stall |
|
warnings, zero to disable. If both stall_cpu |
|
and stall_gp_kthread are specified, the |
|
kthread is starved first, then the CPU. |
|
|
|
rcutorture.stat_interval= [KNL] |
|
Time (s) between statistics printk()s. |
|
|
|
rcutorture.stutter= [KNL] |
|
Time (s) to stutter testing, for example, specifying |
|
five seconds causes the test to run for five seconds, |
|
wait for five seconds, and so on. This tests RCU's |
|
ability to transition abruptly to and from idle. |
|
|
|
rcutorture.test_boost= [KNL] |
|
Test RCU priority boosting? 0=no, 1=maybe, 2=yes. |
|
"Maybe" means test if the RCU implementation |
|
under test support RCU priority boosting. |
|
|
|
rcutorture.test_boost_duration= [KNL] |
|
Duration (s) of each individual boost test. |
|
|
|
rcutorture.test_boost_interval= [KNL] |
|
Interval (s) between each boost test. |
|
|
|
rcutorture.test_no_idle_hz= [KNL] |
|
Test RCU's dyntick-idle handling. See also the |
|
rcutorture.shuffle_interval parameter. |
|
|
|
rcutorture.torture_type= [KNL] |
|
Specify the RCU implementation to test. |
|
|
|
rcutorture.verbose= [KNL] |
|
Enable additional printk() statements. |
|
|
|
rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] |
|
Dump ftrace buffer after reporting RCU CPU |
|
stall warning. |
|
|
|
rcupdate.rcu_cpu_stall_suppress= [KNL] |
|
Suppress RCU CPU stall warning messages. |
|
|
|
rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] |
|
Suppress RCU CPU stall warning messages and |
|
rcutorture writer stall warnings that occur |
|
during early boot, that is, during the time |
|
before the init task is spawned. |
|
|
|
rcupdate.rcu_cpu_stall_timeout= [KNL] |
|
Set timeout for RCU CPU stall warning messages. |
|
|
|
rcupdate.rcu_expedited= [KNL] |
|
Use expedited grace-period primitives, for |
|
example, synchronize_rcu_expedited() instead |
|
of synchronize_rcu(). This reduces latency, |
|
but can increase CPU utilization, degrade |
|
real-time latency, and degrade energy efficiency. |
|
No effect on CONFIG_TINY_RCU kernels. |
|
|
|
rcupdate.rcu_normal= [KNL] |
|
Use only normal grace-period primitives, |
|
for example, synchronize_rcu() instead of |
|
synchronize_rcu_expedited(). This improves |
|
real-time latency, CPU utilization, and |
|
energy efficiency, but can expose users to |
|
increased grace-period latency. This parameter |
|
overrides rcupdate.rcu_expedited. No effect on |
|
CONFIG_TINY_RCU kernels. |
|
|
|
rcupdate.rcu_normal_after_boot= [KNL] |
|
Once boot has completed (that is, after |
|
rcu_end_inkernel_boot() has been invoked), use |
|
only normal grace-period primitives. No effect |
|
on CONFIG_TINY_RCU kernels. |
|
|
|
But note that CONFIG_PREEMPT_RT=y kernels enables |
|
this kernel boot parameter, forcibly setting |
|
it to the value one, that is, converting any |
|
post-boot attempt at an expedited RCU grace |
|
period to instead use normal non-expedited |
|
grace-period processing. |
|
|
|
rcupdate.rcu_task_ipi_delay= [KNL] |
|
Set time in jiffies during which RCU tasks will |
|
avoid sending IPIs, starting with the beginning |
|
of a given grace period. Setting a large |
|
number avoids disturbing real-time workloads, |
|
but lengthens grace periods. |
|
|
|
rcupdate.rcu_task_stall_timeout= [KNL] |
|
Set timeout in jiffies for RCU task stall warning |
|
messages. Disable with a value less than or equal |
|
to zero. |
|
|
|
rcupdate.rcu_self_test= [KNL] |
|
Run the RCU early boot self tests |
|
|
|
rdinit= [KNL] |
|
Format: <full_path> |
|
Run specified binary instead of /init from the ramdisk, |
|
used for early userspace startup. See initrd. |
|
|
|
rdrand= [X86] |
|
force - Override the decision by the kernel to hide the |
|
advertisement of RDRAND support (this affects |
|
certain AMD processors because of buggy BIOS |
|
support, specifically around the suspend/resume |
|
path). |
|
|
|
rdt= [HW,X86,RDT] |
|
Turn on/off individual RDT features. List is: |
|
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, |
|
mba. |
|
E.g. to turn on cmt and turn off mba use: |
|
rdt=cmt,!mba |
|
|
|
reboot= [KNL] |
|
Format (x86 or x86_64): |
|
[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ |
|
[[,]s[mp]#### \ |
|
[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ |
|
[[,]f[orce] |
|
Where reboot_mode is one of warm (soft) or cold (hard) or gpio |
|
(prefix with 'panic_' to set mode for panic |
|
reboot only), |
|
reboot_type is one of bios, acpi, kbd, triple, efi, or pci, |
|
reboot_force is either force or not specified, |
|
reboot_cpu is s[mp]#### with #### being the processor |
|
to be used for rebooting. |
|
|
|
refscale.holdoff= [KNL] |
|
Set test-start holdoff period. The purpose of |
|
this parameter is to delay the start of the |
|
test until boot completes in order to avoid |
|
interference. |
|
|
|
refscale.loops= [KNL] |
|
Set the number of loops over the synchronization |
|
primitive under test. Increasing this number |
|
reduces noise due to loop start/end overhead, |
|
but the default has already reduced the per-pass |
|
noise to a handful of picoseconds on ca. 2020 |
|
x86 laptops. |
|
|
|
refscale.nreaders= [KNL] |
|
Set number of readers. The default value of -1 |
|
selects N, where N is roughly 75% of the number |
|
of CPUs. A value of zero is an interesting choice. |
|
|
|
refscale.nruns= [KNL] |
|
Set number of runs, each of which is dumped onto |
|
the console log. |
|
|
|
refscale.readdelay= [KNL] |
|
Set the read-side critical-section duration, |
|
measured in microseconds. |
|
|
|
refscale.scale_type= [KNL] |
|
Specify the read-protection implementation to test. |
|
|
|
refscale.shutdown= [KNL] |
|
Shut down the system at the end of the performance |
|
test. This defaults to 1 (shut it down) when |
|
refscale is built into the kernel and to 0 (leave |
|
it running) when refscale is built as a module. |
|
|
|
refscale.verbose= [KNL] |
|
Enable additional printk() statements. |
|
|
|
refscale.verbose_batched= [KNL] |
|
Batch the additional printk() statements. If zero |
|
(the default) or negative, print everything. Otherwise, |
|
print every Nth verbose statement, where N is the value |
|
specified. |
|
|
|
relax_domain_level= |
|
[KNL, SMP] Set scheduler's default relax_domain_level. |
|
See Documentation/admin-guide/cgroup-v1/cpusets.rst. |
|
|
|
reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory |
|
Format: <base1>,<size1>[,<base2>,<size2>,...] |
|
Reserve I/O ports or memory so the kernel won't use |
|
them. If <base> is less than 0x10000, the region |
|
is assumed to be I/O ports; otherwise it is memory. |
|
|
|
reservetop= [X86-32] |
|
Format: nn[KMG] |
|
Reserves a hole at the top of the kernel virtual |
|
address space. |
|
|
|
reset_devices [KNL] Force drivers to reset the underlying device |
|
during initialization. |
|
|
|
resume= [SWSUSP] |
|
Specify the partition device for software suspend |
|
Format: |
|
{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} |
|
|
|
resume_offset= [SWSUSP] |
|
Specify the offset from the beginning of the partition |
|
given by "resume=" at which the swap header is located, |
|
in <PAGE_SIZE> units (needed only for swap files). |
|
See Documentation/power/swsusp-and-swap-files.rst |
|
|
|
resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to |
|
read the resume files |
|
|
|
resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. |
|
Useful for devices that are detected asynchronously |
|
(e.g. USB and MMC devices). |
|
|
|
hibernate= [HIBERNATION] |
|
noresume Don't check if there's a hibernation image |
|
present during boot. |
|
nocompress Don't compress/decompress hibernation images. |
|
no Disable hibernation and resume. |
|
protect_image Turn on image protection during restoration |
|
(that will set all pages holding image data |
|
during restoration read-only). |
|
|
|
retain_initrd [RAM] Keep initrd memory after extraction |
|
|
|
rfkill.default_state= |
|
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, |
|
etc. communication is blocked by default. |
|
1 Unblocked. |
|
|
|
rfkill.master_switch_mode= |
|
0 The "airplane mode" button does nothing. |
|
1 The "airplane mode" button toggles between everything |
|
blocked and the previous configuration. |
|
2 The "airplane mode" button toggles between everything |
|
blocked and everything unblocked. |
|
|
|
rhash_entries= [KNL,NET] |
|
Set number of hash buckets for route cache |
|
|
|
ring3mwait=disable |
|
[KNL] Disable ring 3 MONITOR/MWAIT feature on supported |
|
CPUs. |
|
|
|
ro [KNL] Mount root device read-only on boot |
|
|
|
rodata= [KNL] |
|
on Mark read-only kernel memory as read-only (default). |
|
off Leave read-only kernel memory writable for debugging. |
|
|
|
rockchip.usb_uart |
|
Enable the uart passthrough on the designated usb port |
|
on Rockchip SoCs. When active, the signals of the |
|
debug-uart get routed to the D+ and D- pins of the usb |
|
port and the regular usb controller gets disabled. |
|
|
|
root= [KNL] Root filesystem |
|
See name_to_dev_t comment in init/do_mounts.c. |
|
|
|
rootdelay= [KNL] Delay (in seconds) to pause before attempting to |
|
mount the root filesystem |
|
|
|
rootflags= [KNL] Set root filesystem mount option string |
|
|
|
rootfstype= [KNL] Set root filesystem type |
|
|
|
rootwait [KNL] Wait (indefinitely) for root device to show up. |
|
Useful for devices that are detected asynchronously |
|
(e.g. USB and MMC devices). |
|
|
|
rproc_mem=nn[KMG][@address] |
|
[KNL,ARM,CMA] Remoteproc physical memory block. |
|
Memory area to be used by remote processor image, |
|
managed by CMA. |
|
|
|
rw [KNL] Mount root device read-write on boot |
|
|
|
S [KNL] Run init in single mode |
|
|
|
s390_iommu= [HW,S390] |
|
Set s390 IOTLB flushing mode |
|
strict |
|
With strict flushing every unmap operation will result in |
|
an IOTLB flush. Default is lazy flushing before reuse, |
|
which is faster. |
|
|
|
sa1100ir [NET] |
|
See drivers/net/irda/sa1100_ir.c. |
|
|
|
sched_verbose [KNL] Enables verbose scheduler debug messages. |
|
|
|
schedstats= [KNL,X86] Enable or disable scheduled statistics. |
|
Allowed values are enable and disable. This feature |
|
incurs a small amount of overhead in the scheduler |
|
but is useful for debugging and performance tuning. |
|
|
|
sched_thermal_decay_shift= |
|
[KNL, SMP] Set a decay shift for scheduler thermal |
|
pressure signal. Thermal pressure signal follows the |
|
default decay period of other scheduler pelt |
|
signals(usually 32 ms but configurable). Setting |
|
sched_thermal_decay_shift will left shift the decay |
|
period for the thermal pressure signal by the shift |
|
value. |
|
i.e. with the default pelt decay period of 32 ms |
|
sched_thermal_decay_shift thermal pressure decay pr |
|
1 64 ms |
|
2 128 ms |
|
and so on. |
|
Format: integer between 0 and 10 |
|
Default is 0. |
|
|
|
scftorture.holdoff= [KNL] |
|
Number of seconds to hold off before starting |
|
test. Defaults to zero for module insertion and |
|
to 10 seconds for built-in smp_call_function() |
|
tests. |
|
|
|
scftorture.longwait= [KNL] |
|
Request ridiculously long waits randomly selected |
|
up to the chosen limit in seconds. Zero (the |
|
default) disables this feature. Please note |
|
that requesting even small non-zero numbers of |
|
seconds can result in RCU CPU stall warnings, |
|
softlockup complaints, and so on. |
|
|
|
scftorture.nthreads= [KNL] |
|
Number of kthreads to spawn to invoke the |
|
smp_call_function() family of functions. |
|
The default of -1 specifies a number of kthreads |
|
equal to the number of CPUs. |
|
|
|
scftorture.onoff_holdoff= [KNL] |
|
Number seconds to wait after the start of the |
|
test before initiating CPU-hotplug operations. |
|
|
|
scftorture.onoff_interval= [KNL] |
|
Number seconds to wait between successive |
|
CPU-hotplug operations. Specifying zero (which |
|
is the default) disables CPU-hotplug operations. |
|
|
|
scftorture.shutdown_secs= [KNL] |
|
The number of seconds following the start of the |
|
test after which to shut down the system. The |
|
default of zero avoids shutting down the system. |
|
Non-zero values are useful for automated tests. |
|
|
|
scftorture.stat_interval= [KNL] |
|
The number of seconds between outputting the |
|
current test statistics to the console. A value |
|
of zero disables statistics output. |
|
|
|
scftorture.stutter_cpus= [KNL] |
|
The number of jiffies to wait between each change |
|
to the set of CPUs under test. |
|
|
|
scftorture.use_cpus_read_lock= [KNL] |
|
Use use_cpus_read_lock() instead of the default |
|
preempt_disable() to disable CPU hotplug |
|
while invoking one of the smp_call_function*() |
|
functions. |
|
|
|
scftorture.verbose= [KNL] |
|
Enable additional printk() statements. |
|
|
|
scftorture.weight_single= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_single() function with a zero |
|
"wait" parameter. A value of -1 selects the |
|
default if all other weights are -1. However, |
|
if at least one weight has some other value, a |
|
value of -1 will instead select a weight of zero. |
|
|
|
scftorture.weight_single_wait= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_single() function with a |
|
non-zero "wait" parameter. See weight_single. |
|
|
|
scftorture.weight_many= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_many() function with a zero |
|
"wait" parameter. See weight_single. |
|
Note well that setting a high probability for |
|
this weighting can place serious IPI load |
|
on the system. |
|
|
|
scftorture.weight_many_wait= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_many() function with a |
|
non-zero "wait" parameter. See weight_single |
|
and weight_many. |
|
|
|
scftorture.weight_all= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_all() function with a zero |
|
"wait" parameter. See weight_single and |
|
weight_many. |
|
|
|
scftorture.weight_all_wait= [KNL] |
|
The probability weighting to use for the |
|
smp_call_function_all() function with a |
|
non-zero "wait" parameter. See weight_single |
|
and weight_many. |
|
|
|
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate |
|
xtime_lock contention on larger systems, and/or RCU lock |
|
contention on all systems with CONFIG_MAXSMP set. |
|
Format: { "0" | "1" } |
|
0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" |
|
1 -- enable. |
|
Note: increases power consumption, thus should only be |
|
enabled if running jitter sensitive (HPC/RT) workloads. |
|
|
|
security= [SECURITY] Choose a legacy "major" security module to |
|
enable at boot. This has been deprecated by the |
|
"lsm=" parameter. |
|
|
|
selinux= [SELINUX] Disable or enable SELinux at boot time. |
|
Format: { "0" | "1" } |
|
See security/selinux/Kconfig help text. |
|
0 -- disable. |
|
1 -- enable. |
|
Default value is 1. |
|
|
|
apparmor= [APPARMOR] Disable or enable AppArmor at boot time |
|
Format: { "0" | "1" } |
|
See security/apparmor/Kconfig help text |
|
0 -- disable. |
|
1 -- enable. |
|
Default value is set via kernel config option. |
|
|
|
serialnumber [BUGS=X86-32] |
|
|
|
shapers= [NET] |
|
Maximal number of shapers. |
|
|
|
simeth= [IA-64] |
|
simscsi= |
|
|
|
slram= [HW,MTD] |
|
|
|
slab_merge [MM] |
|
Enable merging of slabs with similar size when the |
|
kernel is built without CONFIG_SLAB_MERGE_DEFAULT. |
|
|
|
slab_nomerge [MM] |
|
Disable merging of slabs with similar size. May be |
|
necessary if there is some reason to distinguish |
|
allocs to different slabs, especially in hardened |
|
environments where the risk of heap overflows and |
|
layout control by attackers can usually be |
|
frustrated by disabling merging. This will reduce |
|
most of the exposure of a heap attack to a single |
|
cache (risks via metadata attacks are mostly |
|
unchanged). Debug options disable merging on their |
|
own. |
|
For more information see Documentation/vm/slub.rst. |
|
|
|
slab_max_order= [MM, SLAB] |
|
Determines the maximum allowed order for slabs. |
|
A high setting may cause OOMs due to memory |
|
fragmentation. Defaults to 1 for systems with |
|
more than 32MB of RAM, 0 otherwise. |
|
|
|
slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] |
|
Enabling slub_debug allows one to determine the |
|
culprit if slab objects become corrupted. Enabling |
|
slub_debug can create guard zones around objects and |
|
may poison objects when not in use. Also tracks the |
|
last alloc / free. For more information see |
|
Documentation/vm/slub.rst. |
|
|
|
slub_max_order= [MM, SLUB] |
|
Determines the maximum allowed order for slabs. |
|
A high setting may cause OOMs due to memory |
|
fragmentation. For more information see |
|
Documentation/vm/slub.rst. |
|
|
|
slub_min_objects= [MM, SLUB] |
|
The minimum number of objects per slab. SLUB will |
|
increase the slab order up to slub_max_order to |
|
generate a sufficiently large slab able to contain |
|
the number of objects indicated. The higher the number |
|
of objects the smaller the overhead of tracking slabs |
|
and the less frequently locks need to be acquired. |
|
For more information see Documentation/vm/slub.rst. |
|
|
|
slub_min_order= [MM, SLUB] |
|
Determines the minimum page order for slabs. Must be |
|
lower than slub_max_order. |
|
For more information see Documentation/vm/slub.rst. |
|
|
|
slub_merge [MM, SLUB] |
|
Same with slab_merge. |
|
|
|
slub_nomerge [MM, SLUB] |
|
Same with slab_nomerge. This is supported for legacy. |
|
See slab_nomerge for more information. |
|
|
|
smart2= [HW] |
|
Format: <io1>[,<io2>[,...,<io8>]] |
|
|
|
smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices |
|
smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port |
|
smsc-ircc2.ircc_sir= [HW] SIR base I/O port |
|
smsc-ircc2.ircc_fir= [HW] FIR base I/O port |
|
smsc-ircc2.ircc_irq= [HW] IRQ line |
|
smsc-ircc2.ircc_dma= [HW] DMA channel |
|
smsc-ircc2.ircc_transceiver= [HW] Transceiver type: |
|
0: Toshiba Satellite 1800 (GP data pin select) |
|
1: Fast pin select (default) |
|
2: ATC IRMode |
|
|
|
smt [KNL,S390] Set the maximum number of threads (logical |
|
CPUs) to use per physical CPU on systems capable of |
|
symmetric multithreading (SMT). Will be capped to the |
|
actual hardware limit. |
|
Format: <integer> |
|
Default: -1 (no limit) |
|
|
|
softlockup_panic= |
|
[KNL] Should the soft-lockup detector generate panics. |
|
Format: 0 | 1 |
|
|
|
A value of 1 instructs the soft-lockup detector |
|
to panic the machine when a soft-lockup occurs. It is |
|
also controlled by the kernel.softlockup_panic sysctl |
|
and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the |
|
respective build-time switch to that functionality. |
|
|
|
softlockup_all_cpu_backtrace= |
|
[KNL] Should the soft-lockup detector generate |
|
backtraces on all cpus. |
|
Format: 0 | 1 |
|
|
|
sonypi.*= [HW] Sony Programmable I/O Control Device driver |
|
See Documentation/admin-guide/laptops/sonypi.rst |
|
|
|
spectre_v2= [X86] Control mitigation of Spectre variant 2 |
|
(indirect branch speculation) vulnerability. |
|
The default operation protects the kernel from |
|
user space attacks. |
|
|
|
on - unconditionally enable, implies |
|
spectre_v2_user=on |
|
off - unconditionally disable, implies |
|
spectre_v2_user=off |
|
auto - kernel detects whether your CPU model is |
|
vulnerable |
|
|
|
Selecting 'on' will, and 'auto' may, choose a |
|
mitigation method at run time according to the |
|
CPU, the available microcode, the setting of the |
|
CONFIG_RETPOLINE configuration option, and the |
|
compiler with which the kernel was built. |
|
|
|
Selecting 'on' will also enable the mitigation |
|
against user space to user space task attacks. |
|
|
|
Selecting 'off' will disable both the kernel and |
|
the user space protections. |
|
|
|
Specific mitigations can also be selected manually: |
|
|
|
retpoline - replace indirect branches |
|
retpoline,generic - google's original retpoline |
|
retpoline,amd - AMD-specific minimal thunk |
|
|
|
Not specifying this option is equivalent to |
|
spectre_v2=auto. |
|
|
|
spectre_v2_user= |
|
[X86] Control mitigation of Spectre variant 2 |
|
(indirect branch speculation) vulnerability between |
|
user space tasks |
|
|
|
on - Unconditionally enable mitigations. Is |
|
enforced by spectre_v2=on |
|
|
|
off - Unconditionally disable mitigations. Is |
|
enforced by spectre_v2=off |
|
|
|
prctl - Indirect branch speculation is enabled, |
|
but mitigation can be enabled via prctl |
|
per thread. The mitigation control state |
|
is inherited on fork. |
|
|
|
prctl,ibpb |
|
- Like "prctl" above, but only STIBP is |
|
controlled per thread. IBPB is issued |
|
always when switching between different user |
|
space processes. |
|
|
|
seccomp |
|
- Same as "prctl" above, but all seccomp |
|
threads will enable the mitigation unless |
|
they explicitly opt out. |
|
|
|
seccomp,ibpb |
|
- Like "seccomp" above, but only STIBP is |
|
controlled per thread. IBPB is issued |
|
always when switching between different |
|
user space processes. |
|
|
|
auto - Kernel selects the mitigation depending on |
|
the available CPU features and vulnerability. |
|
|
|
Default mitigation: |
|
If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" |
|
|
|
Not specifying this option is equivalent to |
|
spectre_v2_user=auto. |
|
|
|
spec_store_bypass_disable= |
|
[HW] Control Speculative Store Bypass (SSB) Disable mitigation |
|
(Speculative Store Bypass vulnerability) |
|
|
|
Certain CPUs are vulnerable to an exploit against a |
|
a common industry wide performance optimization known |
|
as "Speculative Store Bypass" in which recent stores |
|
to the same memory location may not be observed by |
|
later loads during speculative execution. The idea |
|
is that such stores are unlikely and that they can |
|
be detected prior to instruction retirement at the |
|
end of a particular speculation execution window. |
|
|
|
In vulnerable processors, the speculatively forwarded |
|
store can be used in a cache side channel attack, for |
|
example to read memory to which the attacker does not |
|
directly have access (e.g. inside sandboxed code). |
|
|
|
This parameter controls whether the Speculative Store |
|
Bypass optimization is used. |
|
|
|
On x86 the options are: |
|
|
|
on - Unconditionally disable Speculative Store Bypass |
|
off - Unconditionally enable Speculative Store Bypass |
|
auto - Kernel detects whether the CPU model contains an |
|
implementation of Speculative Store Bypass and |
|
picks the most appropriate mitigation. If the |
|
CPU is not vulnerable, "off" is selected. If the |
|
CPU is vulnerable the default mitigation is |
|
architecture and Kconfig dependent. See below. |
|
prctl - Control Speculative Store Bypass per thread |
|
via prctl. Speculative Store Bypass is enabled |
|
for a process by default. The state of the control |
|
is inherited on fork. |
|
seccomp - Same as "prctl" above, but all seccomp threads |
|
will disable SSB unless they explicitly opt out. |
|
|
|
Default mitigations: |
|
X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" |
|
|
|
On powerpc the options are: |
|
|
|
on,auto - On Power8 and Power9 insert a store-forwarding |
|
barrier on kernel entry and exit. On Power7 |
|
perform a software flush on kernel entry and |
|
exit. |
|
off - No action. |
|
|
|
Not specifying this option is equivalent to |
|
spec_store_bypass_disable=auto. |
|
|
|
spia_io_base= [HW,MTD] |
|
spia_fio_base= |
|
spia_pedr= |
|
spia_peddr= |
|
|
|
split_lock_detect= |
|
[X86] Enable split lock detection or bus lock detection |
|
|
|
When enabled (and if hardware support is present), atomic |
|
instructions that access data across cache line |
|
boundaries will result in an alignment check exception |
|
for split lock detection or a debug exception for |
|
bus lock detection. |
|
|
|
off - not enabled |
|
|
|
warn - the kernel will emit rate-limited warnings |
|
about applications triggering the #AC |
|
exception or the #DB exception. This mode is |
|
the default on CPUs that support split lock |
|
detection or bus lock detection. Default |
|
behavior is by #AC if both features are |
|
enabled in hardware. |
|
|
|
fatal - the kernel will send SIGBUS to applications |
|
that trigger the #AC exception or the #DB |
|
exception. Default behavior is by #AC if |
|
both features are enabled in hardware. |
|
|
|
ratelimit:N - |
|
Set system wide rate limit to N bus locks |
|
per second for bus lock detection. |
|
0 < N <= 1000. |
|
|
|
N/A for split lock detection. |
|
|
|
|
|
If an #AC exception is hit in the kernel or in |
|
firmware (i.e. not while executing in user mode) |
|
the kernel will oops in either "warn" or "fatal" |
|
mode. |
|
|
|
#DB exception for bus lock is triggered only when |
|
CPL > 0. |
|
|
|
srbds= [X86,INTEL] |
|
Control the Special Register Buffer Data Sampling |
|
(SRBDS) mitigation. |
|
|
|
Certain CPUs are vulnerable to an MDS-like |
|
exploit which can leak bits from the random |
|
number generator. |
|
|
|
By default, this issue is mitigated by |
|
microcode. However, the microcode fix can cause |
|
the RDRAND and RDSEED instructions to become |
|
much slower. Among other effects, this will |
|
result in reduced throughput from /dev/urandom. |
|
|
|
The microcode mitigation can be disabled with |
|
the following option: |
|
|
|
off: Disable mitigation and remove |
|
performance impact to RDRAND and RDSEED |
|
|
|
srcutree.counter_wrap_check [KNL] |
|
Specifies how frequently to check for |
|
grace-period sequence counter wrap for the |
|
srcu_data structure's ->srcu_gp_seq_needed field. |
|
The greater the number of bits set in this kernel |
|
parameter, the less frequently counter wrap will |
|
be checked for. Note that the bottom two bits |
|
are ignored. |
|
|
|
srcutree.exp_holdoff [KNL] |
|
Specifies how many nanoseconds must elapse |
|
since the end of the last SRCU grace period for |
|
a given srcu_struct until the next normal SRCU |
|
grace period will be considered for automatic |
|
expediting. Set to zero to disable automatic |
|
expediting. |
|
|
|
ssbd= [ARM64,HW] |
|
Speculative Store Bypass Disable control |
|
|
|
On CPUs that are vulnerable to the Speculative |
|
Store Bypass vulnerability and offer a |
|
firmware based mitigation, this parameter |
|
indicates how the mitigation should be used: |
|
|
|
force-on: Unconditionally enable mitigation for |
|
for both kernel and userspace |
|
force-off: Unconditionally disable mitigation for |
|
for both kernel and userspace |
|
kernel: Always enable mitigation in the |
|
kernel, and offer a prctl interface |
|
to allow userspace to register its |
|
interest in being mitigated too. |
|
|
|
stack_guard_gap= [MM] |
|
override the default stack gap protection. The value |
|
is in page units and it defines how many pages prior |
|
to (for stacks growing down) resp. after (for stacks |
|
growing up) the main stack are reserved for no other |
|
mapping. Default value is 256 pages. |
|
|
|
stack_depot_disable= [KNL] |
|
Setting this to true through kernel command line will |
|
disable the stack depot thereby saving the static memory |
|
consumed by the stack hash table. By default this is set |
|
to false. |
|
|
|
stacktrace [FTRACE] |
|
Enabled the stack tracer on boot up. |
|
|
|
stacktrace_filter=[function-list] |
|
[FTRACE] Limit the functions that the stack tracer |
|
will trace at boot up. function-list is a comma-separated |
|
list of functions. This list can be changed at run |
|
time by the stack_trace_filter file in the debugfs |
|
tracing directory. Note, this enables stack tracing |
|
and the stacktrace above is not needed. |
|
|
|
sti= [PARISC,HW] |
|
Format: <num> |
|
Set the STI (builtin display/keyboard on the HP-PARISC |
|
machines) console (graphic card) which should be used |
|
as the initial boot-console. |
|
See also comment in drivers/video/console/sticore.c. |
|
|
|
sti_font= [HW] |
|
See comment in drivers/video/console/sticore.c. |
|
|
|
stifb= [HW] |
|
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] |
|
|
|
sunrpc.min_resvport= |
|
sunrpc.max_resvport= |
|
[NFS,SUNRPC] |
|
SunRPC servers often require that client requests |
|
originate from a privileged port (i.e. a port in the |
|
range 0 < portnr < 1024). |
|
An administrator who wishes to reserve some of these |
|
ports for other uses may adjust the range that the |
|
kernel's sunrpc client considers to be privileged |
|
using these two parameters to set the minimum and |
|
maximum port values. |
|
|
|
sunrpc.svc_rpc_per_connection_limit= |
|
[NFS,SUNRPC] |
|
Limit the number of requests that the server will |
|
process in parallel from a single connection. |
|
The default value is 0 (no limit). |
|
|
|
sunrpc.pool_mode= |
|
[NFS] |
|
Control how the NFS server code allocates CPUs to |
|
service thread pools. Depending on how many NICs |
|
you have and where their interrupts are bound, this |
|
option will affect which CPUs will do NFS serving. |
|
Note: this parameter cannot be changed while the |
|
NFS server is running. |
|
|
|
auto the server chooses an appropriate mode |
|
automatically using heuristics |
|
global a single global pool contains all CPUs |
|
percpu one pool for each CPU |
|
pernode one pool for each NUMA node (equivalent |
|
to global on non-NUMA machines) |
|
|
|
sunrpc.tcp_slot_table_entries= |
|
sunrpc.udp_slot_table_entries= |
|
[NFS,SUNRPC] |
|
Sets the upper limit on the number of simultaneous |
|
RPC calls that can be sent from the client to a |
|
server. Increasing these values may allow you to |
|
improve throughput, but will also increase the |
|
amount of memory reserved for use by the client. |
|
|
|
suspend.pm_test_delay= |
|
[SUSPEND] |
|
Sets the number of seconds to remain in a suspend test |
|
mode before resuming the system (see |
|
/sys/power/pm_test). Only available when CONFIG_PM_DEBUG |
|
is set. Default value is 5. |
|
|
|
svm= [PPC] |
|
Format: { on | off | y | n | 1 | 0 } |
|
This parameter controls use of the Protected |
|
Execution Facility on pSeries. |
|
|
|
swapaccount=[0|1] |
|
[KNL] Enable accounting of swap in memory resource |
|
controller if no parameter or 1 is given or disable |
|
it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) |
|
|
|
swiotlb= [ARM,IA-64,PPC,MIPS,X86] |
|
Format: { <int> | force | noforce } |
|
<int> -- Number of I/O TLB slabs |
|
force -- force using of bounce buffers even if they |
|
wouldn't be automatically used by the kernel |
|
noforce -- Never use bounce buffers (for debugging) |
|
|
|
switches= [HW,M68k] |
|
|
|
sysctl.*= [KNL] |
|
Set a sysctl parameter, right before loading the init |
|
process, as if the value was written to the respective |
|
/proc/sys/... file. Both '.' and '/' are recognized as |
|
separators. Unrecognized parameters and invalid values |
|
are reported in the kernel log. Sysctls registered |
|
later by a loaded module cannot be set this way. |
|
Example: sysctl.vm.swappiness=40 |
|
|
|
sysfs.deprecated=0|1 [KNL] |
|
Enable/disable old style sysfs layout for old udev |
|
on older distributions. When this option is enabled |
|
very new udev will not work anymore. When this option |
|
is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) |
|
in older udev will not work anymore. |
|
Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in |
|
the kernel configuration. |
|
|
|
sysrq_always_enabled |
|
[KNL] |
|
Ignore sysrq setting - this boot parameter will |
|
neutralize any effect of /proc/sys/kernel/sysrq. |
|
Useful for debugging. |
|
|
|
tcpmhash_entries= [KNL,NET] |
|
Set the number of tcp_metrics_hash slots. |
|
Default value is 8192 or 16384 depending on total |
|
ram pages. This is used to specify the TCP metrics |
|
cache size. See Documentation/networking/ip-sysctl.rst |
|
"tcp_no_metrics_save" section for more details. |
|
|
|
tdfx= [HW,DRM] |
|
|
|
test_suspend= [SUSPEND][,N] |
|
Specify "mem" (for Suspend-to-RAM) or "standby" (for |
|
standby suspend) or "freeze" (for suspend type freeze) |
|
as the system sleep state during system startup with |
|
the optional capability to repeat N number of times. |
|
The system is woken from this state using a |
|
wakeup-capable RTC alarm. |
|
|
|
thash_entries= [KNL,NET] |
|
Set number of hash buckets for TCP connection |
|
|
|
thermal.act= [HW,ACPI] |
|
-1: disable all active trip points in all thermal zones |
|
<degrees C>: override all lowest active trip points |
|
|
|
thermal.crt= [HW,ACPI] |
|
-1: disable all critical trip points in all thermal zones |
|
<degrees C>: override all critical trip points |
|
|
|
thermal.nocrt= [HW,ACPI] |
|
Set to disable actions on ACPI thermal zone |
|
critical and hot trip points. |
|
|
|
thermal.off= [HW,ACPI] |
|
1: disable ACPI thermal control |
|
|
|
thermal.psv= [HW,ACPI] |
|
-1: disable all passive trip points |
|
<degrees C>: override all passive trip points to this |
|
value |
|
|
|
thermal.tzp= [HW,ACPI] |
|
Specify global default ACPI thermal zone polling rate |
|
<deci-seconds>: poll all this frequency |
|
0: no polling (default) |
|
|
|
threadirqs [KNL] |
|
Force threading of all interrupt handlers except those |
|
marked explicitly IRQF_NO_THREAD. |
|
|
|
topology= [S390] |
|
Format: {off | on} |
|
Specify if the kernel should make use of the cpu |
|
topology information if the hardware supports this. |
|
The scheduler will make use of this information and |
|
e.g. base its process migration decisions on it. |
|
Default is on. |
|
|
|
topology_updates= [KNL, PPC, NUMA] |
|
Format: {off} |
|
Specify if the kernel should ignore (off) |
|
topology updates sent by the hypervisor to this |
|
LPAR. |
|
|
|
torture.disable_onoff_at_boot= [KNL] |
|
Prevent the CPU-hotplug component of torturing |
|
until after init has spawned. |
|
|
|
torture.ftrace_dump_at_shutdown= [KNL] |
|
Dump the ftrace buffer at torture-test shutdown, |
|
even if there were no errors. This can be a |
|
very costly operation when many torture tests |
|
are running concurrently, especially on systems |
|
with rotating-rust storage. |
|
|
|
torture.verbose_sleep_frequency= [KNL] |
|
Specifies how many verbose printk()s should be |
|
emitted between each sleep. The default of zero |
|
disables verbose-printk() sleeping. |
|
|
|
torture.verbose_sleep_duration= [KNL] |
|
Duration of each verbose-printk() sleep in jiffies. |
|
|
|
tp720= [HW,PS2] |
|
|
|
tpm_suspend_pcr=[HW,TPM] |
|
Format: integer pcr id |
|
Specify that at suspend time, the tpm driver |
|
should extend the specified pcr with zeros, |
|
as a workaround for some chips which fail to |
|
flush the last written pcr on TPM_SaveState. |
|
This will guarantee that all the other pcrs |
|
are saved. |
|
|
|
trace_buf_size=nn[KMG] |
|
[FTRACE] will set tracing buffer size on each cpu. |
|
|
|
trace_event=[event-list] |
|
[FTRACE] Set and start specified trace events in order |
|
to facilitate early boot debugging. The event-list is a |
|
comma-separated list of trace events to enable. See |
|
also Documentation/trace/events.rst |
|
|
|
trace_options=[option-list] |
|
[FTRACE] Enable or disable tracer options at boot. |
|
The option-list is a comma delimited list of options |
|
that can be enabled or disabled just as if you were |
|
to echo the option name into |
|
|
|
/sys/kernel/debug/tracing/trace_options |
|
|
|
For example, to enable stacktrace option (to dump the |
|
stack trace of each event), add to the command line: |
|
|
|
trace_options=stacktrace |
|
|
|
See also Documentation/trace/ftrace.rst "trace options" |
|
section. |
|
|
|
tp_printk[FTRACE] |
|
Have the tracepoints sent to printk as well as the |
|
tracing ring buffer. This is useful for early boot up |
|
where the system hangs or reboots and does not give the |
|
option for reading the tracing buffer or performing a |
|
ftrace_dump_on_oops. |
|
|
|
To turn off having tracepoints sent to printk, |
|
echo 0 > /proc/sys/kernel/tracepoint_printk |
|
Note, echoing 1 into this file without the |
|
tracepoint_printk kernel cmdline option has no effect. |
|
|
|
The tp_printk_stop_on_boot (see below) can also be used |
|
to stop the printing of events to console at |
|
late_initcall_sync. |
|
|
|
** CAUTION ** |
|
|
|
Having tracepoints sent to printk() and activating high |
|
frequency tracepoints such as irq or sched, can cause |
|
the system to live lock. |
|
|
|
tp_printk_stop_on_boot[FTRACE] |
|
When tp_printk (above) is set, it can cause a lot of noise |
|
on the console. It may be useful to only include the |
|
printing of events during boot up, as user space may |
|
make the system inoperable. |
|
|
|
This command line option will stop the printing of events |
|
to console at the late_initcall_sync() time frame. |
|
|
|
traceoff_on_warning |
|
[FTRACE] enable this option to disable tracing when a |
|
warning is hit. This turns off "tracing_on". Tracing can |
|
be enabled again by echoing '1' into the "tracing_on" |
|
file located in /sys/kernel/debug/tracing/ |
|
|
|
This option is useful, as it disables the trace before |
|
the WARNING dump is called, which prevents the trace to |
|
be filled with content caused by the warning output. |
|
|
|
This option can also be set at run time via the sysctl |
|
option: kernel/traceoff_on_warning |
|
|
|
transparent_hugepage= |
|
[KNL] |
|
Format: [always|madvise|never] |
|
Can be used to control the default behavior of the system |
|
with respect to transparent hugepages. |
|
See Documentation/admin-guide/mm/transhuge.rst |
|
for more details. |
|
|
|
trusted.source= [KEYS] |
|
Format: <string> |
|
This parameter identifies the trust source as a backend |
|
for trusted keys implementation. Supported trust |
|
sources: |
|
- "tpm" |
|
- "tee" |
|
If not specified then it defaults to iterating through |
|
the trust source list starting with TPM and assigns the |
|
first trust source as a backend which is initialized |
|
successfully during iteration. |
|
|
|
tsc= Disable clocksource stability checks for TSC. |
|
Format: <string> |
|
[x86] reliable: mark tsc clocksource as reliable, this |
|
disables clocksource verification at runtime, as well |
|
as the stability checks done at bootup. Used to enable |
|
high-resolution timer mode on older hardware, and in |
|
virtualized environment. |
|
[x86] noirqtime: Do not use TSC to do irq accounting. |
|
Used to run time disable IRQ_TIME_ACCOUNTING on any |
|
platforms where RDTSC is slow and this accounting |
|
can add overhead. |
|
[x86] unstable: mark the TSC clocksource as unstable, this |
|
marks the TSC unconditionally unstable at bootup and |
|
avoids any further wobbles once the TSC watchdog notices. |
|
[x86] nowatchdog: disable clocksource watchdog. Used |
|
in situations with strict latency requirements (where |
|
interruptions from clocksource watchdog are not |
|
acceptable). |
|
|
|
tsc_early_khz= [X86] Skip early TSC calibration and use the given |
|
value instead. Useful when the early TSC frequency discovery |
|
procedure is not reliable, such as on overclocked systems |
|
with CPUID.16h support and partial CPUID.15h support. |
|
Format: <unsigned int> |
|
|
|
tsx= [X86] Control Transactional Synchronization |
|
Extensions (TSX) feature in Intel processors that |
|
support TSX control. |
|
|
|
This parameter controls the TSX feature. The options are: |
|
|
|
on - Enable TSX on the system. Although there are |
|
mitigations for all known security vulnerabilities, |
|
TSX has been known to be an accelerator for |
|
several previous speculation-related CVEs, and |
|
so there may be unknown security risks associated |
|
with leaving it enabled. |
|
|
|
off - Disable TSX on the system. (Note that this |
|
option takes effect only on newer CPUs which are |
|
not vulnerable to MDS, i.e., have |
|
MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get |
|
the new IA32_TSX_CTRL MSR through a microcode |
|
update. This new MSR allows for the reliable |
|
deactivation of the TSX functionality.) |
|
|
|
auto - Disable TSX if X86_BUG_TAA is present, |
|
otherwise enable TSX on the system. |
|
|
|
Not specifying this option is equivalent to tsx=off. |
|
|
|
See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst |
|
for more details. |
|
|
|
tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async |
|
Abort (TAA) vulnerability. |
|
|
|
Similar to Micro-architectural Data Sampling (MDS) |
|
certain CPUs that support Transactional |
|
Synchronization Extensions (TSX) are vulnerable to an |
|
exploit against CPU internal buffers which can forward |
|
information to a disclosure gadget under certain |
|
conditions. |
|
|
|
In vulnerable processors, the speculatively forwarded |
|
data can be used in a cache side channel attack, to |
|
access data to which the attacker does not have direct |
|
access. |
|
|
|
This parameter controls the TAA mitigation. The |
|
options are: |
|
|
|
full - Enable TAA mitigation on vulnerable CPUs |
|
if TSX is enabled. |
|
|
|
full,nosmt - Enable TAA mitigation and disable SMT on |
|
vulnerable CPUs. If TSX is disabled, SMT |
|
is not disabled because CPU is not |
|
vulnerable to cross-thread TAA attacks. |
|
off - Unconditionally disable TAA mitigation |
|
|
|
On MDS-affected machines, tsx_async_abort=off can be |
|
prevented by an active MDS mitigation as both vulnerabilities |
|
are mitigated with the same mechanism so in order to disable |
|
this mitigation, you need to specify mds=off too. |
|
|
|
Not specifying this option is equivalent to |
|
tsx_async_abort=full. On CPUs which are MDS affected |
|
and deploy MDS mitigation, TAA mitigation is not |
|
required and doesn't provide any additional |
|
mitigation. |
|
|
|
For details see: |
|
Documentation/admin-guide/hw-vuln/tsx_async_abort.rst |
|
|
|
turbografx.map[2|3]= [HW,JOY] |
|
TurboGraFX parallel port interface |
|
Format: |
|
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> |
|
See also Documentation/input/devices/joystick-parport.rst |
|
|
|
udbg-immortal [PPC] When debugging early kernel crashes that |
|
happen after console_init() and before a proper |
|
console driver takes over, this boot options might |
|
help "seeing" what's going on. |
|
|
|
uhash_entries= [KNL,NET] |
|
Set number of hash buckets for UDP/UDP-Lite connections |
|
|
|
uhci-hcd.ignore_oc= |
|
[USB] Ignore overcurrent events (default N). |
|
Some badly-designed motherboards generate lots of |
|
bogus events, for ports that aren't wired to |
|
anything. Set this parameter to avoid log spamming. |
|
Note that genuine overcurrent events won't be |
|
reported either. |
|
|
|
unknown_nmi_panic |
|
[X86] Cause panic on unknown NMI. |
|
|
|
usbcore.authorized_default= |
|
[USB] Default USB device authorization: |
|
(default -1 = authorized except for wireless USB, |
|
0 = not authorized, 1 = authorized, 2 = authorized |
|
if device connected to internal port) |
|
|
|
usbcore.autosuspend= |
|
[USB] The autosuspend time delay (in seconds) used |
|
for newly-detected USB devices (default 2). This |
|
is the time required before an idle device will be |
|
autosuspended. Devices for which the delay is set |
|
to a negative value won't be autosuspended at all. |
|
|
|
usbcore.usbfs_snoop= |
|
[USB] Set to log all usbfs traffic (default 0 = off). |
|
|
|
usbcore.usbfs_snoop_max= |
|
[USB] Maximum number of bytes to snoop in each URB |
|
(default = 65536). |
|
|
|
usbcore.blinkenlights= |
|
[USB] Set to cycle leds on hubs (default 0 = off). |
|
|
|
usbcore.old_scheme_first= |
|
[USB] Start with the old device initialization |
|
scheme (default 0 = off). |
|
|
|
usbcore.usbfs_memory_mb= |
|
[USB] Memory limit (in MB) for buffers allocated by |
|
usbfs (default = 16, 0 = max = 2047). |
|
|
|
usbcore.use_both_schemes= |
|
[USB] Try the other device initialization scheme |
|
if the first one fails (default 1 = enabled). |
|
|
|
usbcore.initial_descriptor_timeout= |
|
[USB] Specifies timeout for the initial 64-byte |
|
USB_REQ_GET_DESCRIPTOR request in milliseconds |
|
(default 5000 = 5.0 seconds). |
|
|
|
usbcore.nousb [USB] Disable the USB subsystem |
|
|
|
usbcore.quirks= |
|
[USB] A list of quirk entries to augment the built-in |
|
usb core quirk list. List entries are separated by |
|
commas. Each entry has the form |
|
VendorID:ProductID:Flags. The IDs are 4-digit hex |
|
numbers and Flags is a set of letters. Each letter |
|
will change the built-in quirk; setting it if it is |
|
clear and clearing it if it is set. The letters have |
|
the following meanings: |
|
a = USB_QUIRK_STRING_FETCH_255 (string |
|
descriptors must not be fetched using |
|
a 255-byte read); |
|
b = USB_QUIRK_RESET_RESUME (device can't resume |
|
correctly so reset it instead); |
|
c = USB_QUIRK_NO_SET_INTF (device can't handle |
|
Set-Interface requests); |
|
d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't |
|
handle its Configuration or Interface |
|
strings); |
|
e = USB_QUIRK_RESET (device can't be reset |
|
(e.g morph devices), don't use reset); |
|
f = USB_QUIRK_HONOR_BNUMINTERFACES (device has |
|
more interface descriptions than the |
|
bNumInterfaces count, and can't handle |
|
talking to these interfaces); |
|
g = USB_QUIRK_DELAY_INIT (device needs a pause |
|
during initialization, after we read |
|
the device descriptor); |
|
h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For |
|
high speed and super speed interrupt |
|
endpoints, the USB 2.0 and USB 3.0 spec |
|
require the interval in microframes (1 |
|
microframe = 125 microseconds) to be |
|
calculated as interval = 2 ^ |
|
(bInterval-1). |
|
Devices with this quirk report their |
|
bInterval as the result of this |
|
calculation instead of the exponent |
|
variable used in the calculation); |
|
i = USB_QUIRK_DEVICE_QUALIFIER (device can't |
|
handle device_qualifier descriptor |
|
requests); |
|
j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device |
|
generates spurious wakeup, ignore |
|
remote wakeup capability); |
|
k = USB_QUIRK_NO_LPM (device can't handle Link |
|
Power Management); |
|
l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL |
|
(Device reports its bInterval as linear |
|
frames instead of the USB 2.0 |
|
calculation); |
|
m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs |
|
to be disconnected before suspend to |
|
prevent spurious wakeup); |
|
n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a |
|
pause after every control message); |
|
o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra |
|
delay after resetting its port); |
|
Example: quirks=0781:5580:bk,0a5c:5834:gij |
|
|
|
usbhid.mousepoll= |
|
[USBHID] The interval which mice are to be polled at. |
|
|
|
usbhid.jspoll= |
|
[USBHID] The interval which joysticks are to be polled at. |
|
|
|
usbhid.kbpoll= |
|
[USBHID] The interval which keyboards are to be polled at. |
|
|
|
usb-storage.delay_use= |
|
[UMS] The delay in seconds before a new device is |
|
scanned for Logical Units (default 1). |
|
|
|
usb-storage.quirks= |
|
[UMS] A list of quirks entries to supplement or |
|
override the built-in unusual_devs list. List |
|
entries are separated by commas. Each entry has |
|
the form VID:PID:Flags where VID and PID are Vendor |
|
and Product ID values (4-digit hex numbers) and |
|
Flags is a set of characters, each corresponding |
|
to a common usb-storage quirk flag as follows: |
|
a = SANE_SENSE (collect more than 18 bytes |
|
of sense data, not on uas); |
|
b = BAD_SENSE (don't collect more than 18 |
|
bytes of sense data, not on uas); |
|
c = FIX_CAPACITY (decrease the reported |
|
device capacity by one sector); |
|
d = NO_READ_DISC_INFO (don't use |
|
READ_DISC_INFO command, not on uas); |
|
e = NO_READ_CAPACITY_16 (don't use |
|
READ_CAPACITY_16 command); |
|
f = NO_REPORT_OPCODES (don't use report opcodes |
|
command, uas only); |
|
g = MAX_SECTORS_240 (don't transfer more than |
|
240 sectors at a time, uas only); |
|
h = CAPACITY_HEURISTICS (decrease the |
|
reported device capacity by one |
|
sector if the number is odd); |
|
i = IGNORE_DEVICE (don't bind to this |
|
device); |
|
j = NO_REPORT_LUNS (don't use report luns |
|
command, uas only); |
|
k = NO_SAME (do not use WRITE_SAME, uas only) |
|
l = NOT_LOCKABLE (don't try to lock and |
|
unlock ejectable media, not on uas); |
|
m = MAX_SECTORS_64 (don't transfer more |
|
than 64 sectors = 32 KB at a time, |
|
not on uas); |
|
n = INITIAL_READ10 (force a retry of the |
|
initial READ(10) command, not on uas); |
|
o = CAPACITY_OK (accept the capacity |
|
reported by the device, not on uas); |
|
p = WRITE_CACHE (the device cache is ON |
|
by default, not on uas); |
|
r = IGNORE_RESIDUE (the device reports |
|
bogus residue values, not on uas); |
|
s = SINGLE_LUN (the device has only one |
|
Logical Unit); |
|
t = NO_ATA_1X (don't allow ATA(12) and ATA(16) |
|
commands, uas only); |
|
u = IGNORE_UAS (don't bind to the uas driver); |
|
w = NO_WP_DETECT (don't test whether the |
|
medium is write-protected). |
|
y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE |
|
even if the device claims no cache, |
|
not on uas) |
|
Example: quirks=0419:aaf5:rl,0421:0433:rc |
|
|
|
user_debug= [KNL,ARM] |
|
Format: <int> |
|
See arch/arm/Kconfig.debug help text. |
|
1 - undefined instruction events |
|
2 - system calls |
|
4 - invalid data aborts |
|
8 - SIGSEGV faults |
|
16 - SIGBUS faults |
|
Example: user_debug=31 |
|
|
|
userpte= |
|
[X86] Flags controlling user PTE allocations. |
|
|
|
nohigh = do not allocate PTE pages in |
|
HIGHMEM regardless of setting |
|
of CONFIG_HIGHPTE. |
|
|
|
vdso= [X86,SH] |
|
On X86_32, this is an alias for vdso32=. Otherwise: |
|
|
|
vdso=1: enable VDSO (the default) |
|
vdso=0: disable VDSO mapping |
|
|
|
vdso32= [X86] Control the 32-bit vDSO |
|
vdso32=1: enable 32-bit VDSO |
|
vdso32=0 or vdso32=2: disable 32-bit VDSO |
|
|
|
See the help text for CONFIG_COMPAT_VDSO for more |
|
details. If CONFIG_COMPAT_VDSO is set, the default is |
|
vdso32=0; otherwise, the default is vdso32=1. |
|
|
|
For compatibility with older kernels, vdso32=2 is an |
|
alias for vdso32=0. |
|
|
|
Try vdso32=0 if you encounter an error that says: |
|
dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! |
|
|
|
vector= [IA-64,SMP] |
|
vector=percpu: enable percpu vector domain |
|
|
|
video= [FB] Frame buffer configuration |
|
See Documentation/fb/modedb.rst. |
|
|
|
video.brightness_switch_enabled= [0,1] |
|
If set to 1, on receiving an ACPI notify event |
|
generated by hotkey, video driver will adjust brightness |
|
level and then send out the event to user space through |
|
the allocated input device; If set to 0, video driver |
|
will only send out the event without touching backlight |
|
brightness level. |
|
default: 1 |
|
|
|
virtio_mmio.device= |
|
[VMMIO] Memory mapped virtio (platform) device. |
|
|
|
<size>@<baseaddr>:<irq>[:<id>] |
|
where: |
|
<size> := size (can use standard suffixes |
|
like K, M and G) |
|
<baseaddr> := physical base address |
|
<irq> := interrupt number (as passed to |
|
request_irq()) |
|
<id> := (optional) platform device id |
|
example: |
|
virtio_mmio.device=1K@0x100b0000:48:7 |
|
|
|
Can be used multiple times for multiple devices. |
|
|
|
vga= [BOOT,X86-32] Select a particular video mode |
|
See Documentation/x86/boot.rst and |
|
Documentation/admin-guide/svga.rst. |
|
Use vga=ask for menu. |
|
This is actually a boot loader parameter; the value is |
|
passed to the kernel using a special protocol. |
|
|
|
vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. |
|
May slow down system boot speed, especially when |
|
enabled on systems with a large amount of memory. |
|
All options are enabled by default, and this |
|
interface is meant to allow for selectively |
|
enabling or disabling specific virtual memory |
|
debugging features. |
|
|
|
Available options are: |
|
P Enable page structure init time poisoning |
|
- Disable all of the above options |
|
|
|
vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact |
|
size of <nn>. This can be used to increase the |
|
minimum size (128MB on x86). It can also be used to |
|
decrease the size and leave more room for directly |
|
mapped kernel RAM. |
|
|
|
vmcp_cma=nn[MG] [KNL,S390] |
|
Sets the memory size reserved for contiguous memory |
|
allocations for the vmcp device driver. |
|
|
|
vmhalt= [KNL,S390] Perform z/VM CP command after system halt. |
|
Format: <command> |
|
|
|
vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. |
|
Format: <command> |
|
|
|
vmpoff= [KNL,S390] Perform z/VM CP command after power off. |
|
Format: <command> |
|
|
|
vsyscall= [X86-64] |
|
Controls the behavior of vsyscalls (i.e. calls to |
|
fixed addresses of 0xffffffffff600x00 from legacy |
|
code). Most statically-linked binaries and older |
|
versions of glibc use these calls. Because these |
|
functions are at fixed addresses, they make nice |
|
targets for exploits that can control RIP. |
|
|
|
emulate [default] Vsyscalls turn into traps and are |
|
emulated reasonably safely. The vsyscall |
|
page is readable. |
|
|
|
xonly Vsyscalls turn into traps and are |
|
emulated reasonably safely. The vsyscall |
|
page is not readable. |
|
|
|
none Vsyscalls don't work at all. This makes |
|
them quite hard to use for exploits but |
|
might break your system. |
|
|
|
vt.color= [VT] Default text color. |
|
Format: 0xYX, X = foreground, Y = background. |
|
Default: 0x07 = light gray on black. |
|
|
|
vt.cur_default= [VT] Default cursor shape. |
|
Format: 0xCCBBAA, where AA, BB, and CC are the same as |
|
the parameters of the <Esc>[?A;B;Cc escape sequence; |
|
see VGA-softcursor.txt. Default: 2 = underline. |
|
|
|
vt.default_blu= [VT] |
|
Format: <blue0>,<blue1>,<blue2>,...,<blue15> |
|
Change the default blue palette of the console. |
|
This is a 16-member array composed of values |
|
ranging from 0-255. |
|
|
|
vt.default_grn= [VT] |
|
Format: <green0>,<green1>,<green2>,...,<green15> |
|
Change the default green palette of the console. |
|
This is a 16-member array composed of values |
|
ranging from 0-255. |
|
|
|
vt.default_red= [VT] |
|
Format: <red0>,<red1>,<red2>,...,<red15> |
|
Change the default red palette of the console. |
|
This is a 16-member array composed of values |
|
ranging from 0-255. |
|
|
|
vt.default_utf8= |
|
[VT] |
|
Format=<0|1> |
|
Set system-wide default UTF-8 mode for all tty's. |
|
Default is 1, i.e. UTF-8 mode is enabled for all |
|
newly opened terminals. |
|
|
|
vt.global_cursor_default= |
|
[VT] |
|
Format=<-1|0|1> |
|
Set system-wide default for whether a cursor |
|
is shown on new VTs. Default is -1, |
|
i.e. cursors will be created by default unless |
|
overridden by individual drivers. 0 will hide |
|
cursors, 1 will display them. |
|
|
|
vt.italic= [VT] Default color for italic text; 0-15. |
|
Default: 2 = green. |
|
|
|
vt.underline= [VT] Default color for underlined text; 0-15. |
|
Default: 3 = cyan. |
|
|
|
watchdog timers [HW,WDT] For information on watchdog timers, |
|
see Documentation/watchdog/watchdog-parameters.rst |
|
or other driver-specific files in the |
|
Documentation/watchdog/ directory. |
|
|
|
watchdog_thresh= |
|
[KNL] |
|
Set the hard lockup detector stall duration |
|
threshold in seconds. The soft lockup detector |
|
threshold is set to twice the value. A value of 0 |
|
disables both lockup detectors. Default is 10 |
|
seconds. |
|
|
|
workqueue.watchdog_thresh= |
|
If CONFIG_WQ_WATCHDOG is configured, workqueue can |
|
warn stall conditions and dump internal state to |
|
help debugging. 0 disables workqueue stall |
|
detection; otherwise, it's the stall threshold |
|
duration in seconds. The default value is 30 and |
|
it can be updated at runtime by writing to the |
|
corresponding sysfs file. |
|
|
|
workqueue.disable_numa |
|
By default, all work items queued to unbound |
|
workqueues are affine to the NUMA nodes they're |
|
issued on, which results in better behavior in |
|
general. If NUMA affinity needs to be disabled for |
|
whatever reason, this option can be used. Note |
|
that this also can be controlled per-workqueue for |
|
workqueues visible under /sys/bus/workqueue/. |
|
|
|
workqueue.power_efficient |
|
Per-cpu workqueues are generally preferred because |
|
they show better performance thanks to cache |
|
locality; unfortunately, per-cpu workqueues tend to |
|
be more power hungry than unbound workqueues. |
|
|
|
Enabling this makes the per-cpu workqueues which |
|
were observed to contribute significantly to power |
|
consumption unbound, leading to measurably lower |
|
power usage at the cost of small performance |
|
overhead. |
|
|
|
The default value of this parameter is determined by |
|
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. |
|
|
|
workqueue.debug_force_rr_cpu |
|
Workqueue used to implicitly guarantee that work |
|
items queued without explicit CPU specified are put |
|
on the local CPU. This guarantee is no longer true |
|
and while local CPU is still preferred work items |
|
may be put on foreign CPUs. This debug option |
|
forces round-robin CPU selection to flush out |
|
usages which depend on the now broken guarantee. |
|
When enabled, memory and cache locality will be |
|
impacted. |
|
|
|
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of |
|
default x2apic cluster mode on platforms |
|
supporting x2apic. |
|
|
|
xen_512gb_limit [KNL,X86-64,XEN] |
|
Restricts the kernel running paravirtualized under Xen |
|
to use only up to 512 GB of RAM. The reason to do so is |
|
crash analysis tools and Xen tools for doing domain |
|
save/restore/migration must be enabled to handle larger |
|
domains. |
|
|
|
xen_emul_unplug= [HW,X86,XEN] |
|
Unplug Xen emulated devices |
|
Format: [unplug0,][unplug1] |
|
ide-disks -- unplug primary master IDE devices |
|
aux-ide-disks -- unplug non-primary-master IDE devices |
|
nics -- unplug network devices |
|
all -- unplug all emulated devices (NICs and IDE disks) |
|
unnecessary -- unplugging emulated devices is |
|
unnecessary even if the host did not respond to |
|
the unplug protocol |
|
never -- do not unplug even if version check succeeds |
|
|
|
xen_legacy_crash [X86,XEN] |
|
Crash from Xen panic notifier, without executing late |
|
panic() code such as dumping handler. |
|
|
|
xen_nopvspin [X86,XEN] |
|
Disables the qspinlock slowpath using Xen PV optimizations. |
|
This parameter is obsoleted by "nopvspin" parameter, which |
|
has equivalent effect for XEN platform. |
|
|
|
xen_nopv [X86] |
|
Disables the PV optimizations forcing the HVM guest to |
|
run as generic HVM guest with no PV drivers. |
|
This option is obsoleted by the "nopv" option, which |
|
has equivalent effect for XEN platform. |
|
|
|
xen_no_vector_callback |
|
[KNL,X86,XEN] Disable the vector callback for Xen |
|
event channel interrupts. |
|
|
|
xen_scrub_pages= [XEN] |
|
Boolean option to control scrubbing pages before giving them back |
|
to Xen, for use by other domains. Can be also changed at runtime |
|
with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. |
|
Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. |
|
|
|
xen_timer_slop= [X86-64,XEN] |
|
Set the timer slop (in nanoseconds) for the virtual Xen |
|
timers (default is 100000). This adjusts the minimum |
|
delta of virtualized Xen timers, where lower values |
|
improve timer resolution at the expense of processing |
|
more timer interrupts. |
|
|
|
xen.event_eoi_delay= [XEN] |
|
How long to delay EOI handling in case of event |
|
storms (jiffies). Default is 10. |
|
|
|
xen.event_loop_timeout= [XEN] |
|
After which time (jiffies) the event handling loop |
|
should start to delay EOI handling. Default is 2. |
|
|
|
xen.fifo_events= [XEN] |
|
Boolean parameter to disable using fifo event handling |
|
even if available. Normally fifo event handling is |
|
preferred over the 2-level event handling, as it is |
|
fairer and the number of possible event channels is |
|
much higher. Default is on (use fifo events). |
|
|
|
nopv= [X86,XEN,KVM,HYPER_V,VMWARE] |
|
Disables the PV optimizations forcing the guest to run |
|
as generic guest with no PV drivers. Currently support |
|
XEN HVM, KVM, HYPER_V and VMWARE guest. |
|
|
|
nopvspin [X86,XEN,KVM] |
|
Disables the qspinlock slow path using PV optimizations |
|
which allow the hypervisor to 'idle' the guest on lock |
|
contention. |
|
|
|
xirc2ps_cs= [NET,PCMCIA] |
|
Format: |
|
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] |
|
|
|
xive= [PPC] |
|
By default on POWER9 and above, the kernel will |
|
natively use the XIVE interrupt controller. This option |
|
allows the fallback firmware mode to be used: |
|
|
|
off Fallback to firmware control of XIVE interrupt |
|
controller on both pseries and powernv |
|
platforms. Only useful on POWER9 and above. |
|
|
|
xhci-hcd.quirks [USB,KNL] |
|
A hex value specifying bitmask with supplemental xhci |
|
host controller quirks. Meaning of each bit can be |
|
consulted in header drivers/usb/host/xhci.h. |
|
|
|
xmon [PPC] |
|
Format: { early | on | rw | ro | off } |
|
Controls if xmon debugger is enabled. Default is off. |
|
Passing only "xmon" is equivalent to "xmon=early". |
|
early Call xmon as early as possible on boot; xmon |
|
debugger is called from setup_arch(). |
|
on xmon debugger hooks will be installed so xmon |
|
is only called on a kernel crash. Default mode, |
|
i.e. either "ro" or "rw" mode, is controlled |
|
with CONFIG_XMON_DEFAULT_RO_MODE. |
|
rw xmon debugger hooks will be installed so xmon |
|
is called only on a kernel crash, mode is write, |
|
meaning SPR registers, memory and, other data |
|
can be written using xmon commands. |
|
ro same as "rw" option above but SPR registers, |
|
memory, and other data can't be written using |
|
xmon commands. |
|
off xmon is disabled.
|
|
|