kvm: robustify steal time record

[cascardo/linux.git] / arch / x86 / kvm / x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 96e81d2..57a62d1 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2011,10 +2011,26 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
                &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
                return;
 
+       if (vcpu->arch.st.steal.version & 1)
+               vcpu->arch.st.steal.version += 1;  /* first time write, random junk */
+
+       vcpu->arch.st.steal.version += 1;
+
+       kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+               &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
+
+       smp_wmb();
+
        vcpu->arch.st.steal.steal += current->sched_info.run_delay -
                vcpu->arch.st.last_steal;
        vcpu->arch.st.last_steal = current->sched_info.run_delay;
-       vcpu->arch.st.steal.version += 2;
+
+       kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+               &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
+
+       smp_wmb();
+
+       vcpu->arch.st.steal.version += 1;
 
        kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
                &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));