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 D2701222599; Tue, 3 Mar 2026 00:34:32 +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=1772498072; cv=none; b=YkW9IL9zDDgRblYLiZ4YP18KldI60kBWd3ntFOj5P8/aVYNlFs1IMhhU9x8OAAkdOSbV+EfxtiILsD9a98nxYg63xfLsdUhHW2fis19/Zox8nqwXStFlI7yZZaQrDhwKPeJGVwueZGuW4Dc7p5oqI2hzJZF7BTmbnUu9MpWFAQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772498072; c=relaxed/simple; bh=bzvY4YRGMLfrodijPDFgV86Y9a5hYWOyqUPTjZ20rsE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rTBPmT2go8gE/SDsWwG9TyLNKk8yK/evkDKbH2XhDEwsfydzgRtS6a2RJaPv1q6hlTukbt75Bq4eZgRm0ROQhSdaJdxpQO01fJokymYlacaKt6hb9aYs0bWHtD7mG9OLp8fZyOfdWtBfwFGFPXfLvclfKftQOITSet0N69f+zTM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l654d4/w; 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="l654d4/w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 706E7C2BCAF; Tue, 3 Mar 2026 00:34:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772498072; bh=bzvY4YRGMLfrodijPDFgV86Y9a5hYWOyqUPTjZ20rsE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=l654d4/wAl5yqVTdMpefI8/iCp5hW3OcSK4fsntbm/XeZQI+4gIFYuNCLq1gpu6eN gjPBRoctTJ3Ag4RjmawL/ZYNJ6wuzkldLzqWRwpYQyXlY6IcKFla92QrDAtBcx6bjX nqaTCt90Aa13gUaaKUNes4hdT5E59OauCEe0oIJFs9BZUjaTGA+fCG0OH53AHXdv9B SOI0/LVIGLzOGXdO5MKezyrk9U2mFibD5Mkj+AVv21DOgzn3AV7qWTVd2hCjJrOz3a /gRH3QJ0+Wq1kmH4SzPdEdaOetqt11lUvxAUqAuS/hEJfakA4z2ZYOn/951aHicxCh eOKLw9if3KvZQ== 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 v7 03/26] KVM: SVM: Add missing save/restore handling of LBR MSRs Date: Tue, 3 Mar 2026 00:33:57 +0000 Message-ID: <20260303003421.2185681-4-yosry@kernel.org> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog In-Reply-To: <20260303003421.2185681-1-yosry@kernel.org> References: <20260303003421.2185681-1-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(). For VMX, this also adds save/restore handling of KVM_GET_MSR_INDEX_LIST. For unspported MSR_IA32_LAST* MSRs, kvm_do_msr_access() should 0 these MSRs on userspace reads, and ignore KVM_MSR_RET_UNSUPPORTED on userspace writes. 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 | 5 +++++ arch/x86/kvm/svm/svm.c | 24 ++++++++++++++++++++++++ arch/x86/kvm/x86.c | 3 +++ 3 files changed, 32 insertions(+) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index f7d5db0af69ac..3bf758c9cb85c 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1100,6 +1100,11 @@ 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); + to_save->dbgctl &= ~DEBUGCTL_RESERVED_BITS; + } } 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[] = { -- 2.53.0.473.g4a7958ca14-goog