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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by MN1PEPF0000ECD9.mail.protection.outlook.com (10.167.242.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9203.9 via Frontend Transport; Tue, 7 Oct 2025 08:02:34 +0000 Received: from BLR-L1-NDADHANI (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 7 Oct 2025 01:02:28 -0700 From: Nikunj A Dadhania To: Jim Mattson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , Sean Christopherson , Paolo Bonzini , Pawan Gupta , "Tom Lendacky" , Jim Mattson , "Perry Yuan" , Sohil Mehta , "Xin Li (Intel)" , Joerg Roedel , Avi Kivity , , , Yosry Ahmed Subject: Re: [PATCH v2 2/2] KVM: SVM: Disallow EFER.LMSLE when not supported by hardware In-Reply-To: <20251001001529.1119031-3-jmattson@google.com> References: <20251001001529.1119031-1-jmattson@google.com> <20251001001529.1119031-3-jmattson@google.com> Date: Tue, 7 Oct 2025 08:02:26 +0000 Message-ID: <85o6qjqgvh.fsf@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: satlexmb08.amd.com (10.181.42.217) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN1PEPF0000ECD9:EE_|PH7PR12MB6785:EE_ X-MS-Office365-Filtering-Correlation-Id: b8c94bee-7af4-472b-e453-08de0577dfa9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|36860700013|82310400026|921020; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?T18m69/KuvZxSuFYvsBBAnBdhso6R+8tWgc/OdbXgHMonNVcokzqyB1C7146?= =?us-ascii?Q?jcrrh+kEQ+8H/KkFuoRkSJtCtB4t6mWO2mWLP22tdBsIfQO9b4/mMB1sKgkh?= =?us-ascii?Q?P/Z0rvksqL4Wmg0tlGDMKD8i4tpp/cO4oSw9X/9kyLvP5Zvf1Oj73EiuvUR7?= =?us-ascii?Q?Wu3cTp6yNxI/rJekRODLTPtMinyD3kCoVKB2MvAzWmvoeP+BkSLPtHKf8nVf?= =?us-ascii?Q?ODE0Rpk4cW6sp1MiTI0UamZZTLnGjk5R+oyPTD/ZjLQeXRtQfWnn/DMlSNyg?= =?us-ascii?Q?QNRUyNmj3fykUN1pC/cUhPtU4DMOC7OvbCvoFhJX/tSXFE5LgwnvB0jL8o5B?= =?us-ascii?Q?uUtwcrHcpE6SbSjK4dOmMmNvQb54/wx21FWpIP8YWWi9g4C4Ewy2ufJCH+Qz?= =?us-ascii?Q?qhk/8ecDQqUZ9vqECAYi87/DAxBN+Rj1mhU2QZcAGlKseZUTd2drE1xYFy3l?= =?us-ascii?Q?3tFVcrRgGk5/QO9UZ9qLUCUaunaOl8L634z4pO5OevOj7tsBrEK7V75q9FNt?= =?us-ascii?Q?4FqoULQYh+hjThmJBPuUp1jqC8R4lBqNvxuRPJQ0Siri6pWu32dL2n5iHSQ/?= =?us-ascii?Q?ygtKu+YZvVhzpTfrM85g/L+u+r4bfXlkkKxFGlCA6bg2b8QSs5eeTBBDlHCT?= =?us-ascii?Q?p3JDiwEiESun/izUBE7RPeHTlxks5hk5SKYgv456PYafEDzTxjf/hLBb89pe?= =?us-ascii?Q?Uy1EqhQu6z5F57flArEbObr1kjPRbhBF4qJIEqxaGjCI3FZo8nqStjxPp/md?= =?us-ascii?Q?fRAJzHsLnH+DGuj07GLFKjTEblpM63ydVkWuxPHpYiRQbhJjkRCDQ5IMXDk6?= =?us-ascii?Q?zwcibXmEGS0nPe6aRX8DtZvV+zrSC2/dxsUtW1eFTqFqigAEcXLNvnICh4zy?= =?us-ascii?Q?reRdA3pL+aXwwMWzsd3Te66lboJH7PTCoY8KBluF2cShQBHB12TxI2XSXK8b?= =?us-ascii?Q?wovkFni3TNmy63GhmygbDRaRBGeOYtc9xKFZOoxWG3F//kEtP75XlR84dKgh?= =?us-ascii?Q?9DDztnL6bu2c0wPzB0LbQIGeXwEKaW5ikuNl388l5j+4bM+4M5Qcb6iynJxz?= =?us-ascii?Q?A9AxhpTR46wtBpQTqIgYyYWbRstFpdpQZH503Ju8PRuHnvVDwh2NSuDV6DrY?= =?us-ascii?Q?iBQgkFhOQcUtAupgBXxEaO2ege/5a0PsbbCkm3+dksMNAw7xA0yruPLjssSN?= =?us-ascii?Q?EBi8kGWzyX6q8JM48Ksy42o6XnpVzAVKsg6/E8mZewYuTuFZWwiSUmtCDhsl?= =?us-ascii?Q?VXYDhqWEXOUkK1XSFgtwgSgjZmEYhUcQiWnBXk86vC6FkBnZrLw1gwwlB3ay?= =?us-ascii?Q?G+1YZQoVpYdowAoUSZXktzUlwhNCpLOoEdAOp7EqStbtb79jS/7Q30QL/0ed?= =?us-ascii?Q?VPpKNEyVQJIT0kmprme7gjIrdXXE8YUJ2QR/hy0vR/yYrwJ05UyS0FDF7EO9?= =?us-ascii?Q?ulU3QT9WF+RgIqbOV01EGuK/dfXDV7QijYGpTAK92oQPHlKZzgr0tSKwqEh1?= =?us-ascii?Q?QSZLHTBOYD0zzSE8GM2mfkgKLB3wkiU7X1mloPNX7oI/gJXuLzuC/5vPwt4R?= =?us-ascii?Q?16QHn9irYgwOYA488oovUfe0m83AaX17wEbVFjwQ?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(376014)(7416014)(1800799024)(36860700013)(82310400026)(921020);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Oct 2025 08:02:34.4454 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b8c94bee-7af4-472b-e453-08de0577dfa9 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000ECD9.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6785 Jim Mattson writes: > Modern AMD CPUs do not support segment limit checks in 64-bit mode > (i.e. EFER.LMSLE must be zero). Do not allow a guest to set EFER.LMSLE > on a CPU that requires the bit to be zero. > > For backwards compatibility, allow EFER.LMSLE to be set on CPUs that > support segment limit checks in 64-bit mode, even though KVM's > implementation of the feature is incomplete (e.g. KVM's emulator does > not enforce segment limits in 64-bit mode). > > Fixes: eec4b140c924 ("KVM: SVM: Allow EFER.LMSLE to be set with nested svm") > > Signed-off-by: Jim Mattson Reviewed-by: Nikunj A Dadhania > --- > arch/x86/kvm/svm/svm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1bfebe40854f..78d0fc85d0bd 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -5351,7 +5351,9 @@ static __init int svm_hardware_setup(void) > > if (nested) { > pr_info("Nested Virtualization enabled\n"); > - kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE); > + kvm_enable_efer_bits(EFER_SVME); > + if (!boot_cpu_has(X86_FEATURE_EFER_LMSLE_MBZ)) > + kvm_enable_efer_bits(EFER_LMSLE); > > r = nested_svm_init_msrpm_merge_offsets(); > if (r) > -- > 2.51.0.618.g983fd99d29-goog