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Subject[PATCH 06/12] x86/pvclock: make sure rdtsc doesn't speculate out of region
Date
rdtsc is not necessarily ordered with surrounding instructions so we
need to make sure that it doesn't get sampled out of order with
respect to reading the time_info.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Glauber Costa <gcosta@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
---
arch/x86/kernel/pvclock.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 03801f2..963f349 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -117,10 +117,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)

do {
version = pvclock_get_time_values(&shadow, src);
- barrier();
+ rdtsc_barrier();
offset = pvclock_get_nsec_offset(&shadow);
ret = shadow.system_timestamp + offset;
- barrier();
+ rdtsc_barrier();
} while (version != src->version);

return ret;
--
1.6.2.5


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