Commit 16a96021 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Paolo Bonzini

KVM: x86: disable master clock if TSC is reset during suspend

Updating system_time from the kernel clock once master clock
has been enabled can result in time backwards event, in case
kernel clock frequency is lower than TSC frequency.

Disable master clock in case it is necessary to update it
from the resume path.
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5367742a
...@@ -106,6 +106,8 @@ EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz); ...@@ -106,6 +106,8 @@ EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);
static u32 tsc_tolerance_ppm = 250; static u32 tsc_tolerance_ppm = 250;
module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR); module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR);
static bool backwards_tsc_observed = false;
#define KVM_NR_SHARED_MSRS 16 #define KVM_NR_SHARED_MSRS 16
struct kvm_shared_msrs_global { struct kvm_shared_msrs_global {
...@@ -1486,7 +1488,8 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm) ...@@ -1486,7 +1488,8 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm)
&ka->master_kernel_ns, &ka->master_kernel_ns,
&ka->master_cycle_now); &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) if (ka->use_master_clock)
atomic_set(&kvm_guest_has_master_clock, 1); atomic_set(&kvm_guest_has_master_clock, 1);
...@@ -6945,6 +6948,7 @@ int kvm_arch_hardware_enable(void *garbage) ...@@ -6945,6 +6948,7 @@ int kvm_arch_hardware_enable(void *garbage)
*/ */
if (backwards_tsc) { if (backwards_tsc) {
u64 delta_cyc = max_tsc - local_tsc; u64 delta_cyc = max_tsc - local_tsc;
backwards_tsc_observed = true;
list_for_each_entry(kvm, &vm_list, vm_list) { list_for_each_entry(kvm, &vm_list, vm_list) {
kvm_for_each_vcpu(i, vcpu, kvm) { kvm_for_each_vcpu(i, vcpu, kvm) {
vcpu->arch.tsc_offset_adjustment += delta_cyc; vcpu->arch.tsc_offset_adjustment += delta_cyc;
......
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