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KVM: SVM: Disable preemption across AVIC load/put during APICv refresh

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Disable preemption when loading/putting the AVIC during an APICv refresh.
If the vCPU task is preempted and migrated ot a different pCPU, the
unprotected avic_vcpu_load() could set the wrong pCPU in the physical ID
cache/table.

Pull the necessary code out of avic_vcpu_{,un}blocking() and into a new
helper to reduce the probability of introducing this exact bug a third
time.

Fixes: df7e4827c5 ("KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC")
Cc: stable@vger.kernel.org
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2022-03-01 09:05:09 -08:00
committed by Paolo Bonzini
parent aa9f58415a
commit b652de1e3d
3 changed files with 59 additions and 50 deletions
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4
arch/x86/kvm/svm/svm.c
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@@ -1318,13 +1318,13 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
indirect_branch_prediction_barrier();
}
if (kvm_vcpu_apicv_active(vcpu))
avic_vcpu_load(vcpu, cpu);
__avic_vcpu_load(vcpu, cpu);
}
static void svm_vcpu_put(struct kvm_vcpu *vcpu)
{
if (kvm_vcpu_apicv_active(vcpu))
avic_vcpu_put(vcpu);
__avic_vcpu_put(vcpu);
svm_prepare_host_switch(vcpu);