From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH] x86/pvclock-xen: zero last_value on resume Date: Fri, 26 Nov 2010 14:29:40 -0800 Message-ID: <4CF034D4.70005@goop.org> References: <4CC708DE.1070000@goop.org> <4CEACFAB.90503@goop.org> <20101126104047.GA9798@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20101126104047.GA9798@elte.hu> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ingo Molnar Cc: "Xen-devel@lists.xensource.com" , kvm-devel , Glauber Costa , the arch/x86 maintainers , Linux Kernel Mailing List , Linux Virtualization , Olivier Hanesse , Avi Kivity , "H. Peter Anvin" , Thomas Gleixner , Eelco Dolstra List-Id: xen-devel@lists.xenproject.org On 11/26/2010 02:40 AM, Ingo Molnar wrote: > * Jeremy Fitzhardinge wrote: > >> 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. > Does not apply cleanly here - mind resending the latest version? It rebased cleanly to 2.6.37-rc3. You can pull it from: git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git pvclock-resume Jeremy Fitzhardinge (1): x86/pvclock: zero last_value on resume arch/x86/include/asm/pvclock.h | 1 + arch/x86/kernel/pvclock.c | 5 +++++ arch/x86/xen/time.c | 2 ++ 3 files changed, 8 insertions(+), 0 deletions(-) Thanks, J Subject: [PATCH] x86/pvclock: zero last_value on resume 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. Signed-off-by: Jeremy Fitzhardinge diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h index 7f7e577..31d84ac 100644 --- a/arch/x86/include/asm/pvclock.h +++ b/arch/x86/include/asm/pvclock.h @@ -11,6 +11,7 @@ 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); /* * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 008b91e..42eb330 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -83,6 +83,11 @@ 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;