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88 lines
2.2 KiB
88 lines
2.2 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Hyper-V specific spinlock code. |
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* |
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* Copyright (C) 2018, Intel, Inc. |
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* |
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* Author : Yi Sun <[email protected]> |
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*/ |
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#define pr_fmt(fmt) "Hyper-V: " fmt |
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#include <linux/spinlock.h> |
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#include <asm/mshyperv.h> |
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#include <asm/paravirt.h> |
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#include <asm/apic.h> |
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static bool __initdata hv_pvspin = true; |
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static void hv_qlock_kick(int cpu) |
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{ |
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apic->send_IPI(cpu, X86_PLATFORM_IPI_VECTOR); |
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} |
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static void hv_qlock_wait(u8 *byte, u8 val) |
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{ |
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unsigned long msr_val; |
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unsigned long flags; |
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if (in_nmi()) |
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return; |
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/* |
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* Reading HV_X64_MSR_GUEST_IDLE MSR tells the hypervisor that the |
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* vCPU can be put into 'idle' state. This 'idle' state is |
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* terminated by an IPI, usually from hv_qlock_kick(), even if |
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* interrupts are disabled on the vCPU. |
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* |
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* To prevent a race against the unlock path it is required to |
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* disable interrupts before accessing the HV_X64_MSR_GUEST_IDLE |
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* MSR. Otherwise, if the IPI from hv_qlock_kick() arrives between |
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* the lock value check and the rdmsrl() then the vCPU might be put |
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* into 'idle' state by the hypervisor and kept in that state for |
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* an unspecified amount of time. |
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*/ |
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local_irq_save(flags); |
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/* |
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* Only issue the rdmsrl() when the lock state has not changed. |
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*/ |
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if (READ_ONCE(*byte) == val) |
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rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val); |
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local_irq_restore(flags); |
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} |
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/* |
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* Hyper-V does not support this so far. |
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*/ |
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__visible bool hv_vcpu_is_preempted(int vcpu) |
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{ |
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return false; |
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} |
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PV_CALLEE_SAVE_REGS_THUNK(hv_vcpu_is_preempted); |
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void __init hv_init_spinlocks(void) |
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{ |
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if (!hv_pvspin || !apic || |
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!(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) || |
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!(ms_hyperv.features & HV_MSR_GUEST_IDLE_AVAILABLE)) { |
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pr_info("PV spinlocks disabled\n"); |
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return; |
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} |
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pr_info("PV spinlocks enabled\n"); |
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__pv_init_lock_hash(); |
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pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath; |
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pv_ops.lock.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); |
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pv_ops.lock.wait = hv_qlock_wait; |
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pv_ops.lock.kick = hv_qlock_kick; |
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pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(hv_vcpu_is_preempted); |
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} |
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static __init int hv_parse_nopvspin(char *arg) |
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{ |
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hv_pvspin = false; |
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return 0; |
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} |
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early_param("hv_nopvspin", hv_parse_nopvspin);
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