[Xen-devel] Re: [PATCH] x86/pvclock-xen: zero last_value on resume

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 10/26/2010 09:59 AM, Jeremy Fitzhardinge wrote:
>
> If the guest domain has been suspend/resumed or migrated, then the
> system clock backing the pvclock clocksource may revert to a smaller
> value (ie, can be non-monotonic across the migration/save-restore).
> Make sure we zero last_value in that case so that the domain
> continues to see clock updates.

Ping?  Looks like this fell through the gaps.

    J

> [ I don't know if kvm needs an analogous fix or not. ]
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> Cc: Stable Kernel <stable@xxxxxxxxxx>
> Reported-by: Eelco Dolstra <e.dolstra@xxxxxxxxxx>
> Reported-by: Olivier Hanesse <olivier.hanesse@xxxxxxxxx>
> Bisected-by: CÃdric Schieli <cschieli@xxxxxxxxx>
> Tested-by: CÃdric Schieli <cschieli@xxxxxxxxx>
>
> diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
> index cd02f32..6226870 100644
> --- a/arch/x86/include/asm/pvclock.h
> +++ b/arch/x86/include/asm/pvclock.h
> @@ -11,5 +11,6 @@ unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info 
> *src);
>  void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
>                           struct pvclock_vcpu_time_info *vcpu,
>                           struct timespec *ts);
> +void pvclock_resume(void);
>  
>  #endif /* _ASM_X86_PVCLOCK_H */
> diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
> index 239427c..a4f07c1 100644
> --- a/arch/x86/kernel/pvclock.c
> +++ b/arch/x86/kernel/pvclock.c
> @@ -120,6 +120,11 @@ unsigned long pvclock_tsc_khz(struct 
> pvclock_vcpu_time_info *src)
>  
>  static atomic64_t last_value = ATOMIC64_INIT(0);
>  
> +void pvclock_resume(void)
> +{
> +     atomic64_set(&last_value, 0);
> +}
> +
>  cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
>  {
>       struct pvclock_shadow_time shadow;
> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
> index b2bb5aa..5da5e53 100644
> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -426,6 +426,8 @@ void xen_timer_resume(void)
>  {
>       int cpu;
>  
> +     pvclock_resume();
> +
>       if (xen_clockevent != &xen_vcpuop_clockevent)
>               return;
>  
>
>
>
>
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