| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.15 070/207] KVM: fix avic_set_running for preemptable kernels | Date | Mon, 6 Dec 2021 15:55:24 +0100 |
| |
From: Paolo Bonzini <pbonzini@redhat.com>
commit 7cfc5c653b07782e7059527df8dc1e3143a7591e upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/kvm/svm/avic.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -988,16 +988,18 @@ 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)
|