Commit 1151a1ef authored by Naman Jain's avatar Naman Jain Committed by Wen Zhiwei
Browse files

x86/hyperv: Fix hv tsc page based sched_clock for hibernation 

stable inclusion
from stable-v6.6.71
commit a6923798e471570ac1b24086be0a9679f51c3171
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBOHV1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a6923798e471570ac1b24086be0a9679f51c3171



--------------------------------

[ Upstream commit bcc80dec91ee745b3d66f3e48f0ec2efdea97149 ]

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 commit e5313f1c ("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: 1349401f ("clocksource/drivers/hyper-v: Suspend/resume Hyper-V clocksource for hibernation")
Co-developed-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarNaman Jain <namjain@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240917053917.76787-1-namjain@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Message-ID: <20240917053917.76787-1-namjain@linux.microsoft.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 47ff774c

arch/x86/kernel/cpu/mshyperv.c

+58 −0
Original line number Diff line number Diff line
@@ -224,6 +224,63 @@ static void hv_machine_crash_shutdown(struct pt_regs *regs) 
	hyperv_cleanup();

}

#endif /* CONFIG_CRASH_DUMP */



static u64 hv_ref_counter_at_suspend;

static void (*old_save_sched_clock_state)(void);

static void (*old_restore_sched_clock_state)(void);



/*

 * Hyper-V clock counter resets during hibernation. Save and restore clock

 * offset during suspend/resume, while also considering the time passed

 * before suspend. This is to make sure that sched_clock using hv tsc page

 * based clocksource, proceeds from where it left off during suspend and

 * it shows correct time for the timestamps of kernel messages after resume.

 */

static void save_hv_clock_tsc_state(void)

{

	hv_ref_counter_at_suspend = hv_read_reference_counter();

}



static void restore_hv_clock_tsc_state(void)

{

	/*

	 * Adjust the offsets used by hv tsc clocksource to

	 * account for the time spent before hibernation.

	 * adjusted value = reference counter (time) at suspend

	 *                - reference counter (time) now.

	 */

	hv_adj_sched_clock_offset(hv_ref_counter_at_suspend - hv_read_reference_counter());

}



/*

 * Functions to override save_sched_clock_state and restore_sched_clock_state

 * functions of x86_platform. The Hyper-V clock counter is reset during

 * suspend-resume and the offset used to measure time needs to be

 * corrected, post resume.

 */

static void hv_save_sched_clock_state(void)

{

	old_save_sched_clock_state();

	save_hv_clock_tsc_state();

}



static void hv_restore_sched_clock_state(void)

{

	restore_hv_clock_tsc_state();

	old_restore_sched_clock_state();

}



static void __init x86_setup_ops_for_tsc_pg_clock(void)

{

	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))

		return;



	old_save_sched_clock_state = x86_platform.save_sched_clock_state;

	x86_platform.save_sched_clock_state = hv_save_sched_clock_state;



	old_restore_sched_clock_state = x86_platform.restore_sched_clock_state;

	x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state;

}

#endif /* CONFIG_HYPERV */



static uint32_t  __init ms_hyperv_platform(void)
@@ -578,6 +635,7 @@ static void __init ms_hyperv_init_platform(void) 


	/* Register Hyper-V specific clocksource */

	hv_init_clocksource();

	x86_setup_ops_for_tsc_pg_clock();

	hv_vtl_init_platform();

#endif

	/*

drivers/clocksource/hyperv_timer.c

+13 −1
Original line number Diff line number Diff line
@@ -27,7 +27,8 @@ 
#include <asm/mshyperv.h>



static struct clock_event_device __percpu *hv_clock_event;

static u64 hv_sched_clock_offset __ro_after_init;

/* Note: offset can hold negative values after hibernation. */

static u64 hv_sched_clock_offset __read_mostly;



/*

 * If false, we're using the old mechanism for stimer0 interrupts
@@ -456,6 +457,17 @@ static void resume_hv_clock_tsc(struct clocksource *arg) 
	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);

}



/*

 * Called during resume from hibernation, from overridden

 * x86_platform.restore_sched_clock_state routine. This is to adjust offsets

 * used to calculate time for hv tsc page based sched_clock, to account for

 * time spent before hibernation.

 */

void hv_adj_sched_clock_offset(u64 offset)

{

	hv_sched_clock_offset -= offset;

}



#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK

static int hv_cs_enable(struct clocksource *cs)

{

include/clocksource/hyperv_timer.h

+2 −0
Original line number Diff line number Diff line
@@ -38,6 +38,8 @@ extern void hv_remap_tsc_clocksource(void); 
extern unsigned long hv_get_tsc_pfn(void);

extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);



extern void hv_adj_sched_clock_offset(u64 offset);



static __always_inline bool

hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,

		     u64 *cur_tsc, u64 *time)