avic_set_running() passes the current CPU to avic_vcpu_load(), albeit
via vcpu->cpu rather than smp_processor_id(). If the thread is migrated
while avic_set_running runs, the call to avic_vcpu_load() can use a stale
value for the processor id. Avoid this by blocking preemption over the
entire execution of avic_set_running().
Reported-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/svm/avic.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 0a58283005f3..560807a2edd4 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1000,16 +1000,18 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
{
struct vcpu_svm *svm = to_svm(vcpu);
+ int cpu = get_cpu();
+ WARN_ON(cpu != vcpu->cpu);
svm->avic_is_running = is_run;
- if (!kvm_vcpu_apicv_active(vcpu))
- return;
-
- if (is_run)
- avic_vcpu_load(vcpu, vcpu->cpu);
- else
- avic_vcpu_put(vcpu);
+ if (kvm_vcpu_apicv_active(vcpu)) {
+ if (is_run)
+ avic_vcpu_load(vcpu, cpu);
+ else
+ avic_vcpu_put(vcpu);
+ }
+ put_cpu();
}
void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
--
2.31.1
