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KVM: fix avic_set_running for preemptable kernels

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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@google.com>
Fixes: 8221c1370056 ("svm: Manage vcpu load/unload when enable AVIC")
Cc: stable@vger.kernel.org
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-11-30 03:46:07 -05:00
parent e90e51d5f0
commit 7cfc5c653b
1 changed files with 9 additions and 7 deletions
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16
arch/x86/kvm/svm/avic.c
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@ -989,16 +989,18 @@ 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)