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>

diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 42eb330..12e47e2 100644 (file)
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -97,10 +97,10 @@ 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);
 
        if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&