@@ -394,6 +394,7 @@ struct kvm_vcpu_arch {
u64 last_tsc_nsec;
u64 last_tsc_write;
u64 last_host_tsc;
+ u64 tsc_offset_adjustment;
bool tsc_catchup;
bool tsc_always_catchup;
s8 virtual_tsc_shift;
@@ -2152,6 +2152,14 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
}
kvm_x86_ops->vcpu_load(vcpu, cpu);
+
+ /* Apply any externally detected TSC adjustments (due to suspend) */
+ if (unlikely(vcpu->arch.tsc_offset_adjustment)) {
+ adjust_tsc_offset_host(vcpu, vcpu->arch.tsc_offset_adjustment);
+ vcpu->arch.tsc_offset_adjustment = 0;
+ set_bit(KVM_REQ_CLOCK_UPDATE,&vcpu->requests);
+ }
+
if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
/* Make sure TSC doesn't go backwards */
s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
@@ -6221,13 +6229,88 @@ int kvm_arch_hardware_enable(void *garbage)
struct kvm *kvm;
struct kvm_vcpu *vcpu;
int i;
+ int ret;
+ u64 local_tsc;
+ u64 max_tsc = 0;
+ bool stable, backwards_tsc = false;
kvm_shared_msr_cpu_online();
- list_for_each_entry(kvm,&vm_list, vm_list)
- kvm_for_each_vcpu(i, vcpu, kvm)
- if (vcpu->cpu == smp_processor_id())
- kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
- return kvm_x86_ops->hardware_enable(garbage);
+ ret = kvm_x86_ops->hardware_enable(garbage);
+ if (ret != 0)
+ return ret;
+
+ local_tsc = native_read_tsc();
+ stable = !check_tsc_unstable();
+ list_for_each_entry(kvm,&vm_list, vm_list) {
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (!stable&& vcpu->cpu == smp_processor_id())
+ set_bit(KVM_REQ_CLOCK_UPDATE,&vcpu->requests);
+ if (stable&& vcpu->arch.last_host_tsc> local_tsc) {
+ backwards_tsc = true;
+ if (vcpu->arch.last_host_tsc> max_tsc)
+ max_tsc = vcpu->arch.last_host_tsc;
+ }
+ }
+ }
+
+ /*
+ * Sometimes, even reliable TSCs go backwards. This happens on
+ * platforms that reset TSC during suspend or hibernate actions, but
+ * maintain synchronization. We must compensate. Fortunately, we can
+ * detect that condition here, which happens early in CPU bringup,
+ * before any KVM threads can be running. Unfortunately, we can't
+ * bring the TSCs fully up to date with real time, as we aren't yet far
+ * enough into CPU bringup that we know how much real time has actually
+ * elapsed; our helper function, get_kernel_ns() will be using boot
+ * variables that haven't been updated yet.
+ *
+ * So we simply find the maximum observed TSC above, then record the
+ * adjustment to TSC in each VCPU. When the VCPU later gets loaded,
+ * the adjustment will be applied. Note that we accumulate
+ * adjustments, in case multiple suspend cycles happen before some VCPU
+ * gets a chance to run again. In the event that no KVM threads get a
+ * chance to run, we will miss the entire elapsed period, as we'll have
+ * reset last_host_tsc, so VCPUs will not have the TSC adjusted and may
+ * loose cycle time. This isn't too big a deal, since the loss will be
+ * uniform across all VCPUs (not to mention the scenario is extremely
+ * unlikely). It is possible that a second hibernate recovery happens
+ * much faster than a first, causing the observed TSC here to be
+ * smaller; this would require additional padding adjustment, which is
+ * why we set last_host_tsc to the local tsc observed here.
+ *
+ * N.B. - this code below runs only on platforms with reliable TSC,
+ * as that is the only way backwards_tsc is set above. Also note
+ * that this runs for ALL vcpus, which is not a bug; all VCPUs should
+ * have the same delta_cyc adjustment applied if backwards_tsc
+ * is detected. Note further, this adjustment is only done once,
+ * as we reset last_host_tsc on all VCPUs to stop this from being
+ * called multiple times (one for each physical CPU bringup).
+ *
+ * Platforms with unnreliable TSCs don't have to deal with this, they
+ * will be compensated by the logic in vcpu_load, which sets the TSC to
+ * catchup mode. This will catchup all VCPUs to real time, but cannot
+ * guarantee that they stay in perfect synchronization.
+ */
+ if (backwards_tsc) {
+ u64 delta_cyc = max_tsc - local_tsc;
+ list_for_each_entry(kvm,&vm_list, vm_list) {
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ vcpu->arch.tsc_offset_adjustment += delta_cyc;
+ vcpu->arch.last_host_tsc = local_tsc;
+ }
+
+ /*
+ * We have to disable TSC offset matching.. if you were
+ * booting a VM while issuing an S4 host suspend....
+ * you may have some problem. Solving this issue is
+ * left as an exercise to the reader.
+ */
+ kvm->arch.last_tsc_nsec = 0;
+ kvm->arch.last_tsc_write = 0;
+ }
+
+ }
+ return 0;
}
void kvm_arch_hardware_disable(void *garbage)