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 C7DB834DB44; Tue, 24 Feb 2026 22:34:22 +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=1771972462; cv=none; b=i9oI84Md4XNthoNlxfS/T8fYYGp3EW0iecMs3po4vMlaugF9GsVUqg5dlLsp5xsjYHlOBuhX3fanuTgWodY3AKRUBABmYiJAfW+h63sn+4/9lQ0N28Q2sPBRndt9vTan++mu6aLeuY1YiRxwL2jJvEAfwJSEAWDf6xKsirCZQUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771972462; c=relaxed/simple; bh=TQeKGqoqKxkagIjzDzM1UTz/dPro9Gug3QNtz5J/bNk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lJJ9OBOLtuwQabRHfHcPutAM7nzmV+bFjTGhk+fH8Y1ylc9lty6YozaxxmupdSliww2OVke3W1vd9pIY0+Q3bYurlkRO3YYuz1KU2ObvrgnivbTfWoBNP8vvN0ACzULNd4+DmgGlPNZJ+60kfQSFXdbsDuINMx0iplyeCJyGlTY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Mle5tSWp; 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="Mle5tSWp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67A6DC19424; Tue, 24 Feb 2026 22:34:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771972462; bh=TQeKGqoqKxkagIjzDzM1UTz/dPro9Gug3QNtz5J/bNk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Mle5tSWp7zF1prFhF7Bb6gPlj3gmrNqrfM0FdCUXk7Q3yAp2ZZPojLIVJYxpEBMat nRxpmFTtkyx3kyPWXBd+tskcBMLtRO6uhqnOKOt6zC9hrsbndJVIwZTAQ7Z1CYUI4R AnO/ouNzavm9FLZbgDiHrtua83pUf8Y8YFB8zaTpJZX4O8nccmYR/y4BnmAIN+1Nqt XiSRanGMFmqzSmtq9GW97qe6+D41fv4z9Z9ce4akzfZHV5OZ3Rm/dkFU69eNJVDZ7A LCcACrO92NyyrNGhq+6/94BMJsMQYHJLeMHuXrXfn27Tp4h3gATARuq5icnLgu8DUo WHisPIcDB7CJQ== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , stable@vger.kernel.org, Jim Mattson Subject: [PATCH v6 03/31] KVM: SVM: Add missing save/restore handling of LBR MSRs Date: Tue, 24 Feb 2026 22:33:37 +0000 Message-ID: <20260224223405.3270433-4-yosry@kernel.org> X-Mailer: git-send-email 2.53.0.414.gf7e9f6c205-goog In-Reply-To: <20260224223405.3270433-1-yosry@kernel.org> References: <20260224223405.3270433-1-yosry@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So save/restore is completely broken. Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to LBR MSRs from userspace only (as they are read-only MSRs). Additionally, to correctly restore L1's LBRs while L2 is running, make sure the LBRs are copied from the captured VMCB01 save area in svm_copy_vmrun_state(). Fixes: 24e09cbf480a ("KVM: SVM: enable LBR virtualization") Cc: stable@vger.kernel.org Reported-by: Jim Mattson Signed-off-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 3 +++ arch/x86/kvm/svm/svm.c | 24 ++++++++++++++++++++++++ arch/x86/kvm/x86.c | 3 +++ 3 files changed, 30 insertions(+) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index f7d5db0af69ac..52d8536845927 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1100,6 +1100,9 @@ void svm_copy_vmrun_state(struct vmcb_save_area *to_save, to_save->isst_addr = from_save->isst_addr; to_save->ssp = from_save->ssp; } + + if (lbrv) + svm_copy_lbrs(to_save, from_save); } void svm_copy_vmloadsave_state(struct vmcb *to_vmcb, struct vmcb *from_vmcb) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index f52e588317fcf..cb53174583a26 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3071,6 +3071,30 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) vmcb_mark_dirty(svm->vmcb, VMCB_LBR); svm_update_lbrv(vcpu); break; + case MSR_IA32_LASTBRANCHFROMIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.br_from = data; + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); + break; + case MSR_IA32_LASTBRANCHTOIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.br_to = data; + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); + break; + case MSR_IA32_LASTINTFROMIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.last_excp_from = data; + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); + break; + case MSR_IA32_LASTINTTOIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.last_excp_to = data; + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); + break; case MSR_VM_HSAVE_PA: /* * Old kernels did not validate the value written to diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index db3f393192d94..416899b5dbe4d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -351,6 +351,9 @@ static const u32 msrs_to_save_base[] = { MSR_IA32_U_CET, MSR_IA32_S_CET, MSR_IA32_PL0_SSP, MSR_IA32_PL1_SSP, MSR_IA32_PL2_SSP, MSR_IA32_PL3_SSP, MSR_IA32_INT_SSP_TAB, + MSR_IA32_DEBUGCTLMSR, + MSR_IA32_LASTBRANCHFROMIP, MSR_IA32_LASTBRANCHTOIP, + MSR_IA32_LASTINTFROMIP, MSR_IA32_LASTINTTOIP, }; static const u32 msrs_to_save_pmu[] = { -- 2.53.0.414.gf7e9f6c205-goog