[PATCH 1/5] x86/pvclock: make sure rdtsc doesn't speculate out of region

Jeremy Fitzhardinge
2009-10-06T00:50:57Z

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>
---
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