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bcc80dec91
read_hv_sched_clock_tsc() assumes that the Hyper-V clock counter is bigger than the variable hv_sched_clock_offset, which is cached during early boot, but depending on the timing this assumption may be false when a hibernated VM starts again (the clock counter starts from 0 again) and is resuming back (Note: hv_init_tsc_clocksource() is not called during hibernation/resume); consequently, read_hv_sched_clock_tsc() may return a negative integer (which is interpreted as a huge positive integer since the return type is u64) and new kernel messages are prefixed with huge timestamps before read_hv_sched_clock_tsc() grows big enough (which typically takes several seconds). Fix the issue by saving the Hyper-V clock counter just before the suspend, and using it to correct the hv_sched_clock_offset in resume. This makes hv tsc page based sched_clock continuous and ensures that post resume, it starts from where it left off during suspend. Override x86_platform.save_sched_clock_state and x86_platform.restore_sched_clock_state routines to correct this as soon as possible. Note: if Invariant TSC is available, the issue doesn't happen because 1) we don't register read_hv_sched_clock_tsc() for sched clock: See commite5313f1c54("clocksource/drivers/hyper-v: Rework clocksource and sched clock setup"); 2) the common x86 code adjusts TSC similarly: see __restore_processor_state() -> tsc_verify_tsc_adjust(true) and x86_platform.restore_sched_clock_state(). Cc: stable@vger.kernel.org Fixes:1349401ff1("clocksource/drivers/hyper-v: Suspend/resume Hyper-V clocksource for hibernation") Co-developed-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Naman Jain <namjain@linux.microsoft.com> Reviewed-by: Michael Kelley <mhklinux@outlook.com> Link: https://lore.kernel.org/r/20240917053917.76787-1-namjain@linux.microsoft.com Signed-off-by: Wei Liu <wei.liu@kernel.org> Message-ID: <20240917053917.76787-1-namjain@linux.microsoft.com>
118 lines
3.3 KiB
C
118 lines
3.3 KiB
C
/* 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 <mikelley@microsoft.com>
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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/hyperv-tlfs.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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#include <asm/hyperv_timer.h>
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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 void hv_remap_tsc_clocksource(void);
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extern unsigned long hv_get_tsc_pfn(void);
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extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
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extern void hv_adj_sched_clock_offset(u64 offset);
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static __always_inline bool
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hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
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u64 *cur_tsc, u64 *time)
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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 false;
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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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*time = mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
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return true;
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}
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#else /* CONFIG_HYPERV_TIMER */
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static inline unsigned long hv_get_tsc_pfn(void)
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{
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return 0;
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}
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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 __always_inline bool
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hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time)
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{
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return false;
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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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