[34-longterm 095/247] x86/pvclock: Zero last_value on resume

Paul Gortmaker
2011-06-23T17:36:20Z

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

commit e7a3481c0246c8e45e79c629efd63b168e91fcda upstream.

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 <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
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(-)

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 53235fd..daaacab 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -10,5 +10,6 @@ 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 dfdfe46..b12fe8d 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -111,6 +111,11 @@ 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 e90360f..a05bda6 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -425,6 +425,8 @@ void xen_timer_resume(void)
{
int cpu;

+ pvclock_resume();
+
if (xen_clockevent != &xen_vcpuop_clockevent)
return;

--
1.7.4.4