From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 A8CB4330B05 for ; Mon, 15 Dec 2025 19:28:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765826883; cv=none; b=bzrhSZ0fXIQ3o30e8crwISxjgIZQGA3obStgUaI6DKgjYhBFhEYq8vNujHXqiGk7LUU3L2uzQgdf7Dh/tv7dHvLmEjqpwO6X/S+umsouq7VrYGT/TCyIVnI1qaZzxqtiZoGzb0ovwYDCOoRsT5IDItg4+SCg981//Jc/H4HV5lQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765826883; c=relaxed/simple; bh=XE5MqLC/E+c3nfSUA3F5tCiRCxkHRh7gjLTo9pofjGc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P0gtLxPvwzetdNXzuQZ5HnH1Y2AJR5e6s8kvxqRgFPyhRcQqdVhUA9/O03FB98/hoOwh2xj3g2MsET2uaIh8PaFerOqyEBbXLAjNqp2RNVzfUY+C3MdMVKwtgRwpnkRRaYgjONXPGmR/ml3Vb+jkgnfXb1blCxBd7yGI3Jiohdc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=UwEeT2J7; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="UwEeT2J7" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1765826874; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MO6FdFw/IPODc9De8JcSe1h5GPGVFOSQkGsv4GnOPzs=; b=UwEeT2J7lp3mwWnNqFLUx3QfBTflu3mNzV6JbyXq9wviYzZA3dTSkfx1axdcRM9yKfF43u KgNEOJvsxFaqT6/66iHTdWW0B0qXDoP9sGPLYt1aG517yL63SWcHpz/qGSury5rt8M91nB kKIXEt2wO4hFJg2mSLedSXglSymmw9k= From: Yosry Ahmed To: Paolo Bonzini , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , stable@vger.kernel.org, Jim Mattson Subject: [PATCH v3 02/26] KVM: SVM: Add missing save/restore handling of LBR MSRs Date: Mon, 15 Dec 2025 19:26:57 +0000 Message-ID: <20251215192722.3654335-4-yosry.ahmed@linux.dev> In-Reply-To: <20251215192722.3654335-1-yosry.ahmed@linux.dev> References: <20251215192722.3654335-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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 | 20 ++++++++++++++++++++ arch/x86/kvm/x86.c | 3 +++ 3 files changed, 26 insertions(+) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 8e157ffbf4b1..53b149dbc930 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1057,6 +1057,9 @@ 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 2428b772546f..2bfc46f22485 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2999,6 +2999,26 @@ 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; + break; + case MSR_IA32_LASTBRANCHTOIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.br_to = data; + break; + case MSR_IA32_LASTINTFROMIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.last_excp_from = data; + break; + case MSR_IA32_LASTINTTOIP: + if (!msr->host_initiated) + return 1; + svm->vmcb->save.last_excp_to = data; + 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 ff8812f3a129..b3d4a8d06689 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -345,6 +345,9 @@ 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[] = { -- 2.52.0.239.gd5f0c6e74e-goog