From: Maciej S. Szmigiero Date: Mon, 25 Aug 2025 16:44:28 +0000 (+0200) Subject: KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active X-Git-Tag: v6.17-rc7~19^2~1^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d02e48830e3fce9701265f6c5a58d9bdaf906a76;p=thirdparty%2Fkernel%2Fstable.git KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active Commit 3bbf3565f48c ("svm: Do not intercept CR8 when enable AVIC") inhibited pre-VMRUN sync of TPR from LAPIC into VMCB::V_TPR in sync_lapic_to_cr8() when AVIC is active. AVIC does automatically sync between these two fields, however it does so only on explicit guest writes to one of these fields, not on a bare VMRUN. This meant that when AVIC is enabled host changes to TPR in the LAPIC state might not get automatically copied into the V_TPR field of VMCB. This is especially true when it is the userspace setting LAPIC state via KVM_SET_LAPIC ioctl() since userspace does not have access to the guest VMCB. Practice shows that it is the V_TPR that is actually used by the AVIC to decide whether to issue pending interrupts to the CPU (not TPR in TASKPRI), so any leftover value in V_TPR will cause serious interrupt delivery issues in the guest when AVIC is enabled. Fix this issue by doing pre-VMRUN TPR sync from LAPIC into VMCB::V_TPR even when AVIC is enabled. Fixes: 3bbf3565f48c ("svm: Do not intercept CR8 when enable AVIC") Cc: stable@vger.kernel.org Signed-off-by: Maciej S. Szmigiero Reviewed-by: Naveen N Rao (AMD) Link: https://lore.kernel.org/r/c231be64280b1461e854e1ce3595d70cde3a2e9d.1756139678.git.maciej.szmigiero@oracle.com [sean: tag for stable@] Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index d9931c6c4bc62..1bfebe40854f4 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4046,8 +4046,7 @@ static inline void sync_lapic_to_cr8(struct kvm_vcpu *vcpu) struct vcpu_svm *svm = to_svm(vcpu); u64 cr8; - if (nested_svm_virtualize_tpr(vcpu) || - kvm_vcpu_apicv_active(vcpu)) + if (nested_svm_virtualize_tpr(vcpu)) return; cr8 = kvm_get_cr8(vcpu);