1 files changed, 14 insertions, 5 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index d57de05dc430..3e1c057e98fe 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -384,13 +384,13 @@ unsigned long native_calibrate_tsc(void)
 {
         u64 tsc1, tsc2, delta, ref1, ref2;
         unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
-        unsigned long flags, latch, ms, fast_calibrate, tsc_khz;
+        unsigned long flags, latch, ms, fast_calibrate, hv_tsc_khz;
         int hpet = is_hpet_enabled(), i, loopmin;
 
-        tsc_khz = get_hypervisor_tsc_freq();
-        if (tsc_khz) {
+        hv_tsc_khz = get_hypervisor_tsc_freq();
+        if (hv_tsc_khz) {
                 printk(KERN_INFO "TSC: Frequency read from the hypervisor\n");
-                return tsc_khz;
+                return hv_tsc_khz;
         }
 
         local_irq_save(flags);
@@ -710,7 +710,16 @@ static cycle_t read_tsc(struct clocksource *cs)
 #ifdef CONFIG_X86_64
 static cycle_t __vsyscall_fn vread_tsc(void)
 {
-        cycle_t ret = (cycle_t)vget_cycles();
+        cycle_t ret;
+
+        /*
+         * Surround the RDTSC by barriers, to make sure it's not
+         * speculated to outside the seqlock critical section and
+         * does not cause time warps:
+         */
+        rdtsc_barrier();
+        ret = (cycle_t)vget_cycles();
+        rdtsc_barrier();
 
         return ret >= __vsyscall_gtod_data.clock.cycle_last ?
                 ret : __vsyscall_gtod_data.clock.cycle_last;