1 files changed, 6 insertions, 2 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8b8fc0b792ba..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 {
@@ -280,7 +282,7 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 }
 EXPORT_SYMBOL_GPL(kvm_set_apic_base);
 
-asmlinkage void kvm_spurious_fault(void)
+asmlinkage __visible void kvm_spurious_fault(void)
 {
         /* Fault while not rebooting.  We want the trace. */
         BUG();
@@ -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;