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 A922B2D0C62 for ; Thu, 20 Nov 2025 18:06:59 +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=1763662019; cv=none; b=ddoPlxz7asFDSG39d4yY9dFCmkqDe2tvct42+lD1jpNwDGNkIh1IqQGd0D+PhvMkK1x78Sy43fquiHjeeDEGbwpttsnmkzHRJg1hTZJPxUZmQY7MrGz42lWQ2S//QQcWYWhlX1BJmrFih1gEbe5WjlfEluUifQRjfKylb7U2sFw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763662019; c=relaxed/simple; bh=sbxQMkJIOSWBcl6/w91i3kpPeiPOT3wVBu8fiDcAp4Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eDy6EEL6edYxa8uPvWHBvZD1KE4Iz+I+cTRldZsuZjJndPo53J+u7Pt95x/zGaVSg41t2i6RFjXpAmQn9lnQf3xdiZdbtxxMFWo8COcflPfriNuiDtaXPE/d7XXK3IPn1UatR+Fw0VVSGrjATnexiWLlQdEMHhl6ubsbLVBb3z4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g6cMMqiH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="g6cMMqiH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EBEBC4CEF1; Thu, 20 Nov 2025 18:06:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763662019; bh=sbxQMkJIOSWBcl6/w91i3kpPeiPOT3wVBu8fiDcAp4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g6cMMqiHHT1l+Ykak6eN5Ce7rqi/a5ZiIHIgmUSTTcgz1P9GBpSvGZnNyWtIGy/nI gdTjfNQut6yagIXnBxb/51k9TQXrcmTel/IdBgOieTLAgRQwJOQNwxdLWoYxpyOLG8 Mrb/b0yBOW5vNen8wGgEFSYfbpXno70KBvbr0NpdrLFKLcM2/8ljn8PWvPvr5DtNZy jfx20LdlYp/4crIug3AS3IpHf6uJq8RTPaCBPSh1a1pSRPtRq5johtnN+02XIOfLLQ Fw0XJMa2uW0qCTrKVybdM5HiB5H1xy34Xdrss5QQU3ZrbBJ+LKTHJT6QmyyT7M2M6f xXvanm1U+IC/Q== From: Sasha Levin To: stable@vger.kernel.org Cc: Yosry Ahmed , Matteo Rizzo , evn@google.com, Jim Mattson , Paolo Bonzini , Sasha Levin Subject: [PATCH 6.1.y] KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated Date: Thu, 20 Nov 2025 13:06:55 -0500 Message-ID: <20251120180655.1918545-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025112036-abdominal-envelope-7ca0@gregkh> References: <2025112036-abdominal-envelope-7ca0@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Yosry Ahmed [ Upstream commit dc55b3c3f61246e483e50c85d8d5366f9567e188 ] The APM lists the DbgCtlMsr field as being tracked by the VMCB_LBR clean bit. Always clear the bit when MSR_IA32_DEBUGCTLMSR is updated. The history is complicated, it was correctly cleared for L1 before commit 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running"). At that point svm_set_msr() started to rely on svm_update_lbrv() to clear the bit, but when nested virtualization is enabled the latter does not always clear it even if MSR_IA32_DEBUGCTLMSR changed. Go back to clearing it directly in svm_set_msr(). Fixes: 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running") Reported-by: Matteo Rizzo Reported-by: evn@google.com Co-developed-by: Jim Mattson Signed-off-by: Jim Mattson Signed-off-by: Yosry Ahmed Link: https://patch.msgid.link/20251108004524.1600006-2-yosry.ahmed@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini [ Open coded svm_get_lbr_vmcb() call ] Signed-off-by: Sasha Levin --- arch/x86/kvm/svm/svm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index f56dcbbbf7341..00fb1c18e23a8 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3053,11 +3053,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) if (data & DEBUGCTL_RESERVED_BITS) return 1; - if (svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK) + if (svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK) { + if (svm->vmcb->save.dbgctl == data) + break; svm->vmcb->save.dbgctl = data; - else + } else { + if (svm->vmcb01.ptr->save.dbgctl == data) + break; svm->vmcb01.ptr->save.dbgctl = data; + } + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); svm_update_lbrv(vcpu); break; -- 2.51.0