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Commit 48434c20 authored by Zachary Amsden's avatar Zachary Amsden Committed by Avi Kivity
Browse files

KVM: x86: Fix deep C-state TSC desynchronization 



When CPUs with unstable TSCs enter deep C-state, TSC may stop
running.  This causes us to require resynchronization.  Since
we can't tell when this may potentially happen, we assume the
worst by forcing re-compensation for it at every point the VCPU
task is descheduled.

Signed-off-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent e48672fa

arch/x86/kvm/x86.c

+1 −1
Original line number Diff line number Diff line
@@ -1866,7 +1866,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
	}



	kvm_x86_ops->vcpu_load(vcpu, cpu);

	if (unlikely(vcpu->cpu != cpu)) {

	if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {

		/* Make sure TSC doesn't go backwards */

		s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :

				native_read_tsc() - vcpu->arch.last_host_tsc;