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-rw-r--r--arch/x86/kvm/x86.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b6c0bacca9bd..20316c67b824 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -106,6 +106,8 @@ EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);
static u32 tsc_tolerance_ppm = 250;
module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR);
+static bool backwards_tsc_observed = false;
+
#define KVM_NR_SHARED_MSRS 16
struct kvm_shared_msrs_global {
@@ -1486,7 +1488,8 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm)
&ka->master_kernel_ns,
&ka->master_cycle_now);
- ka->use_master_clock = host_tsc_clocksource & vcpus_matched;
+ ka->use_master_clock = host_tsc_clocksource && vcpus_matched
+ && !backwards_tsc_observed;
if (ka->use_master_clock)
atomic_set(&kvm_guest_has_master_clock, 1);
@@ -6945,6 +6948,7 @@ int kvm_arch_hardware_enable(void *garbage)
*/
if (backwards_tsc) {
u64 delta_cyc = max_tsc - local_tsc;
+ backwards_tsc_observed = true;
list_for_each_entry(kvm, &vm_list, vm_list) {
kvm_for_each_vcpu(i, vcpu, kvm) {
vcpu->arch.tsc_offset_adjustment += delta_cyc;