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-rw-r--r--arch/x86/kernel/tsc.c19
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;