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112 lines
3.2 KiB
112 lines
3.2 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* Definitions for the clocksource provided by the Hyper-V |
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* hypervisor to guest VMs, as described in the Hyper-V Top |
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* Level Functional Spec (TLFS). |
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* |
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* Copyright (C) 2019, Microsoft, Inc. |
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* |
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* Author: Michael Kelley <[email protected]> |
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*/ |
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#ifndef __CLKSOURCE_HYPERV_TIMER_H |
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#define __CLKSOURCE_HYPERV_TIMER_H |
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#include <linux/clocksource.h> |
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#include <linux/math64.h> |
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#include <asm/mshyperv.h> |
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#define HV_MAX_MAX_DELTA_TICKS 0xffffffff |
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#define HV_MIN_DELTA_TICKS 1 |
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#ifdef CONFIG_HYPERV_TIMER |
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/* Routines called by the VMbus driver */ |
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extern int hv_stimer_alloc(bool have_percpu_irqs); |
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extern int hv_stimer_cleanup(unsigned int cpu); |
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extern void hv_stimer_legacy_init(unsigned int cpu, int sint); |
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extern void hv_stimer_legacy_cleanup(unsigned int cpu); |
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extern void hv_stimer_global_cleanup(void); |
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extern void hv_stimer0_isr(void); |
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extern void hv_init_clocksource(void); |
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extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void); |
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static inline notrace u64 |
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hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc) |
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{ |
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u64 scale, offset; |
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u32 sequence; |
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/* |
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* The protocol for reading Hyper-V TSC page is specified in Hypervisor |
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* Top-Level Functional Specification ver. 3.0 and above. To get the |
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* reference time we must do the following: |
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* - READ ReferenceTscSequence |
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* A special '0' value indicates the time source is unreliable and we |
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* need to use something else. The currently published specification |
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* versions (up to 4.0b) contain a mistake and wrongly claim '-1' |
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* instead of '0' as the special value, see commit c35b82ef0294. |
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* - ReferenceTime = |
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* ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset |
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* - READ ReferenceTscSequence again. In case its value has changed |
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* since our first reading we need to discard ReferenceTime and repeat |
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* the whole sequence as the hypervisor was updating the page in |
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* between. |
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*/ |
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do { |
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sequence = READ_ONCE(tsc_pg->tsc_sequence); |
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if (!sequence) |
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return U64_MAX; |
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/* |
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* Make sure we read sequence before we read other values from |
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* TSC page. |
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*/ |
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smp_rmb(); |
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scale = READ_ONCE(tsc_pg->tsc_scale); |
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offset = READ_ONCE(tsc_pg->tsc_offset); |
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*cur_tsc = hv_get_raw_timer(); |
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/* |
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* Make sure we read sequence after we read all other values |
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* from TSC page. |
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*/ |
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smp_rmb(); |
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} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence); |
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return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset; |
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} |
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static inline notrace u64 |
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hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg) |
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{ |
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u64 cur_tsc; |
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return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc); |
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} |
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#else /* CONFIG_HYPERV_TIMER */ |
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static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void) |
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{ |
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return NULL; |
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} |
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static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, |
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u64 *cur_tsc) |
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{ |
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return U64_MAX; |
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} |
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static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; } |
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static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {} |
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static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {} |
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static inline void hv_stimer_global_cleanup(void) {} |
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static inline void hv_stimer0_isr(void) {} |
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#endif /* CONFIG_HYPERV_TIMER */ |
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#endif
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