From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 767F916A956 for ; Sun, 3 May 2026 12:20:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777810822; cv=none; b=kFYPkNWfuvR7G1/f/94mREri2pGu75T3sCLCJqyoBFFvKnkJIJjl86h6AwfL+Mzoh8T6s7VzpV8RJrFn8NaZR0AY/+EwCLiV1QB9C4GgXl1oqhJyQtozYIxazkDCL7kLPfM4Br3Wj2zrWF/mOWSBg5eXlHlR06lklja2yqn14Fs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777810822; c=relaxed/simple; bh=FKUzfnuX5kRsPii9M1oyIKTcKhGngeY2AZdYDZ8OhzU=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=W13xcOqQ9CyyP/OKFwInBoCFcoSqNRK77+c+QKQhmZwehhdZ4T0v9lxUqfoQuRh4nv5x3P/MUL6WO7hru9VxEWB7q47sAd7qjN/F1X/0/miplddVY3msXEJftPxSSuz0m0/hQDWktoLKB3t9HSxVeLEVJDbbqpaFzALbmm/gT0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AWNy5thj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="AWNy5thj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3720C2BCB4; Sun, 3 May 2026 12:20:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777810822; bh=FKUzfnuX5kRsPii9M1oyIKTcKhGngeY2AZdYDZ8OhzU=; h=Subject:To:Cc:From:Date:From; b=AWNy5thjW71wzfJ3Ke79gLhqTfuEvifhBDKymZE20OCiBqMZnIjYju2NiJt9UklGu WQESMWUcygBlSFHXurC88YqGhZyn9+lyuU0lepHwLl5hZ2ea0OUz9KxtCvttWWE6hK mil9Zi6VCtEAQQhn767rGWrZi1Q+IFSP12IbrTZk= Subject: FAILED: patch "[PATCH] KVM: nSVM: Always intercept VMMCALL when L2 is active" failed to apply to 6.6-stable tree To: seanjc@google.com,vkuznets@redhat.com,yosry@kernel.org Cc: From: Date: Sun, 03 May 2026 14:20:19 +0200 Message-ID: <2026050319-frequency-badge-f9fe@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-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 . 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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 33d3617a52f9930d22b2af59f813c2fbdefa6dd5 # git commit -s git send-email --to '' --in-reply-to '2026050319-frequency-badge-f9fe@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 33d3617a52f9930d22b2af59f813c2fbdefa6dd5 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 3 Mar 2026 16:22:23 -0800 Subject: [PATCH] KVM: nSVM: Always intercept VMMCALL when L2 is active Always intercept VMMCALL now that KVM properly synthesizes a #UD as appropriate, i.e. when L1 doesn't want to intercept VMMCALL, to avoid putting L2 into an infinite #UD loop if KVM_X86_QUIRK_FIX_HYPERCALL_INSN is enabled. By letting L2 execute VMMCALL natively and thus #UD, for all intents and purposes KVM morphs the VMMCALL intercept into a #UD intercept (KVM always intercepts #UD). When the hypercall quirk is enabled, KVM "emulates" VMMCALL in response to the #UD by trying to fixup the opcode to the "right" vendor, then restarts the guest, without skipping the VMMCALL. As a result, the guest sees an endless stream of #UDs since it's already executing the correct vendor hypercall instruction, i.e. the emulator doesn't anticipate that the #UD could be due to lack of interception, as opposed to a truly undefined opcode. Fixes: 0d945bd93511 ("KVM: SVM: Don't allow nested guest to VMMCALL into host") Cc: stable@vger.kernel.org Reviewed-by: Yosry Ahmed Reviewed-by: Vitaly Kuznetsov Link: https://patch.msgid.link/20260304002223.1105129-3-seanjc@google.com Signed-off-by: Sean Christopherson diff --git a/arch/x86/kvm/svm/hyperv.h b/arch/x86/kvm/svm/hyperv.h index 9af03970d40c..f70d076911a6 100644 --- a/arch/x86/kvm/svm/hyperv.h +++ b/arch/x86/kvm/svm/hyperv.h @@ -51,10 +51,6 @@ static inline bool nested_svm_is_l2_tlb_flush_hcall(struct kvm_vcpu *vcpu) void svm_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu); #else /* CONFIG_KVM_HYPERV */ static inline void nested_svm_hv_update_vm_vp_ids(struct kvm_vcpu *vcpu) {} -static inline bool nested_svm_l2_tlb_flush_enabled(struct kvm_vcpu *vcpu) -{ - return false; -} static inline bool nested_svm_is_l2_tlb_flush_hcall(struct kvm_vcpu *vcpu) { return false; diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 0f7893a7cb04..fb86f09985e7 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -158,13 +158,6 @@ void recalc_intercepts(struct vcpu_svm *svm) vmcb_clr_intercept(c, INTERCEPT_VINTR); } - /* - * We want to see VMMCALLs from a nested guest only when Hyper-V L2 TLB - * flush feature is enabled. - */ - if (!nested_svm_l2_tlb_flush_enabled(&svm->vcpu)) - vmcb_clr_intercept(c, INTERCEPT_VMMCALL); - for (i = 0; i < MAX_INTERCEPT; i++) c->intercepts[i] |= g->intercepts[i];