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x86: pvclock: make sure rdtsc doesnt speculate out of region 

Originally from Jeremy Fitzhardinge.

pvclock_get_time_values, which contains the memory barriers
will be removed by next patch.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Marcelo Tosatti 2012-11-27 23:28:49 -02:00
parent 7069ed6763
commit b01578de45
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/pvclock.c
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@ -97,10 +97,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
do { do {
version = pvclock_get_time_values(&shadow, src); version = pvclock_get_time_values(&shadow, src);
barrier(); rdtsc_barrier();
offset = pvclock_get_nsec_offset(&shadow); offset = pvclock_get_nsec_offset(&shadow);
ret = shadow.system_timestamp + offset; ret = shadow.system_timestamp + offset;
barrier(); rdtsc_barrier();
} while (version != src->version); } while (version != src->version);
if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&