From 5cefc44e71d3914acf5500a116e33e8bc0b65094 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 30 Nov 2021 03:46:07 -0500 Subject: [PATCH] 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: Sean Christopherson Fixes: af9badde83f5 ("svm: Manage vcpu load/unload when enable AVIC") Cc: stable@vger.kernel.org Reviewed-by: Maxim Levitsky Signed-off-by: Paolo Bonzini --- 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 affc0ea98d302..9d6066eb7c10e 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -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) -- 2.39.5