Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH] KVM: fix avic_set_running for preemptable kernels | Date | Tue, 30 Nov 2021 03:46:44 -0500 |
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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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- 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
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