Commit 7cfc5c65 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: fix avic_set_running for preemptable kernels 



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: default avatarSean Christopherson <seanjc@google.com>
Fixes: 8221c137 ("svm: Manage vcpu load/unload when enable AVIC")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e90e51d5

arch/x86/kvm/svm/avic.c

+9 −7
Original line number Diff line number Diff line
@@ -989,17 +989,19 @@ 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 (kvm_vcpu_apicv_active(vcpu)) {

		if (is_run)

		avic_vcpu_load(vcpu, vcpu->cpu);

			avic_vcpu_load(vcpu, cpu);

		else

			avic_vcpu_put(vcpu);

	}

	put_cpu();

}



void svm_vcpu_blocking(struct kvm_vcpu *vcpu)

{