The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x d02e48830e3fce9701265f6c5a58d9bdaf906a76 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025092122-popper-small-d970@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From d02e48830e3fce9701265f6c5a58d9bdaf906a76 Mon Sep 17 00:00:00 2001 From: "Maciej S. Szmigiero" maciej.szmigiero@oracle.com Date: Mon, 25 Aug 2025 18:44:28 +0200 Subject: [PATCH] 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 maciej.szmigiero@oracle.com Reviewed-by: Naveen N Rao (AMD) naveen@kernel.org Link: https://lore.kernel.org/r/c231be64280b1461e854e1ce3595d70cde3a2e9d.175613967... [sean: tag for stable@] Signed-off-by: Sean Christopherson seanjc@google.com
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index d9931c6c4bc6..1bfebe40854f 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);