linux-kernel - Re: [PATCH] x86/pvclock-xen: zero last_value on resume

Open Source and information security mailing list archives

Date:	Mon, 22 Nov 2010 12:16:43 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"Xen-devel@...ts.xensource.com" <Xen-devel@...ts.xensource.com>,
	kvm-devel <kvm@...r.kernel.org>,
	Glauber Costa <glommer@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	Olivier Hanesse <olivier.hanesse@...il.com>,
	Avi Kivity <avi@...hat.com>,
	Eelco Dolstra <e.dolstra@...elft.nl>
Subject: Re: [PATCH] x86/pvclock-xen: zero last_value on resume

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@...rix.com>
> Cc: Stable Kernel <stable@...nel.org>
> Reported-by: Eelco Dolstra <e.dolstra@...elft.nl>
> Reported-by: Olivier Hanesse <olivier.hanesse@...il.com>
> Bisected-by: Cédric Schieli <cschieli@...il.com>
> Tested-by: Cédric Schieli <cschieli@...il.com>
>
> 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;
>  
>
>
>
>
> _______________________________________________
> Virtualization mailing list
> Virtualization@...ts.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/virtualization

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