[Xen-devel] [PATCH 06/12] x86/pvclock: make sure rdtsc doesn't speculate out of region

[Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>]

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@xxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Glauber Costa <gcosta@xxxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
---
 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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