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Peter Anvin" CC: Subject: [PATCH v6 05/21] x86/bugs: Add attack vector controls for MDS Date: Mon, 7 Jul 2025 13:33:00 -0500 Message-ID: <20250707183316.1349127-6-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250707183316.1349127-1-david.kaplan@amd.com> References: <20250707183316.1349127-1-david.kaplan@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000989E9:EE_|CH1PPF6B6BCC42C:EE_ X-MS-Office365-Filtering-Correlation-Id: 4a7e378c-c34f-4622-758f-08ddbd84c854 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|82310400026|36860700013|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?LzSFBJmIRJWz1NAsX1QADP/bwxZV+ycKRU081HFeUjhCkcv4JF3mF2CVZlcx?= =?us-ascii?Q?67CFLnYZx39gPfu4wXvHO1lOXdaWGlI0h6W6w7R8j+9tUOO8lMBcT5CxGazY?= =?us-ascii?Q?qI1jl2KWKhkq6LA4lSKpOAwrx4IS9KwmPGezUhyta44s3yyl3PHKJqwkmN/J?= =?us-ascii?Q?vR74MgcJ63b2NPK4sLwIZeoxwofQ/D5N3q7q+qwQAd7XXRGI++41F5Nj3UDQ?= =?us-ascii?Q?6QX5MlJqOsBXIVaZIo4qZuo8cjSu4phoUYc166yw5yjdGh830/zTb037ycaO?= =?us-ascii?Q?XTAlFU7m8NtbUYQ1AqpvvQLwRtjXnSxLyRDYyUe4a/0DK2KvkRjdFNyM0wZL?= =?us-ascii?Q?weYZgLSnHvUo+sm0pYdkHAZe7SSl6Xx7w8ExjkcFcZaSqztrrJ+rs1W0yLYw?= =?us-ascii?Q?tfWh/enr5zC4iJGIn3bMoXwPHEkVIkxq3itjOARCdHkRljIhEMsKa323lQqH?= =?us-ascii?Q?oBEJXH08qXOLnAInf9eIZ6BDUa4yWvJA7sOUQV84bfKuIStOOMid8W8QYjhY?= =?us-ascii?Q?2TFldJ6udKqmd4FOiWncztp1SNi0H+bYpl/V9Sbtpk/n6CZUzL6tq2oL9ofB?= =?us-ascii?Q?wt815x3y8gPL2TH6ZdiG2QdbmYv5BJJoOBz9nhPH7xCyhCzCR/HSB885FQ6f?= =?us-ascii?Q?MX3yL5wBdARrp7BSQnG9SGIhyg1ViosgmzIaBbZdF9QKDLjTVHx+utZJkuMO?= =?us-ascii?Q?sWnZyV8S28B+7g9VttDTeU6RqTwW2PfKv1miaeRQdW/hV/HAFwuW++yhONK/?= =?us-ascii?Q?u+xbeO28LC2HysaKFvNvtMsxPYHCr+UGf/afWll6kCUoqGz4KTQ+ZUNnbinG?= =?us-ascii?Q?3B1goEsSJ16741O48ufliYurOofjwVWypHc0NvMUTNI9s6wtIpJu+4pv9cHc?= =?us-ascii?Q?SD4A/ZoDHNa2j1U84hBpPsGfap2WE8uxceQXW6mH2cRJTRKW/BwkDIi5E/FC?= =?us-ascii?Q?cVfs2RNQ5araSCwut0Nn1vSUXH09a2iSVWEVTccDZSH5h3A9blZv5/ZLTB0B?= =?us-ascii?Q?+6ewTHVtKVWM/wcj73AFFmwpCejSlzQOKy0cnO0pdeylyIlIIstqCf63nG62?= =?us-ascii?Q?2pNIcxcUGeZ5mzbhp9N2s8LPSYisbZSi6ic1YiXQbw3ew3p6WnDyn/LgeidC?= =?us-ascii?Q?iarNBUhIHoqrbYKq5vC1hmVl0ErstfWTZAQJFep5P2/5DUeyGLGC6CGmyQeB?= =?us-ascii?Q?wC+o7fnwG3x5nSWqTNUvCUZyKa2z4LJC5gzd8P4gMG9yQZw7dWr7G6D2C03S?= =?us-ascii?Q?zZzvj2El9PJeEXJGnKOhC49ea6AaDhKhCdyzPlzNtB2lmUQT/N6tf7SElSqm?= =?us-ascii?Q?gZdTTc8bZh3dytfJQqmByzmKNqH5PlINdGgkNkb/VIqSgjWppgqtuMh2xIgV?= =?us-ascii?Q?ZbkhnHE+BgE1BuF/0EXMq5RcdQ7dCEtXdTL3fq8jhSX+AHRLDhkqj9X2vbFx?= =?us-ascii?Q?f7wsHPaxTChnvQXoXg42tB6IGhD4px/tkGKxK+I/uGgTqsipx1y4UYXv/MqL?= =?us-ascii?Q?pt+Gi154gglKetQFP9vcmcKbrZwnJBCc4fL7?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(7416014)(376014)(82310400026)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2025 18:33:34.9429 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4a7e378c-c34f-4622-758f-08ddbd84c854 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000989E9.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH1PPF6B6BCC42C Content-Type: text/plain; charset="utf-8" Use attack vector controls to determine if MDS mitigation is required. The global mitigations=3Doff command now simply disables all attack vectors so explicit checking of mitigations=3Doff is no longer needed. If cross-thread attack mitigations are required, disable SMT. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 1fa0704a8694..65d482aa450f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -437,13 +437,17 @@ static bool verw_clear_cpu_buf_mitigation_selected __= ro_after_init; =20 static void __init mds_select_mitigation(void) { - if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) { + if (!boot_cpu_has_bug(X86_BUG_MDS)) { mds_mitigation =3D MDS_MITIGATION_OFF; return; } =20 - if (mds_mitigation =3D=3D MDS_MITIGATION_AUTO) - mds_mitigation =3D MDS_MITIGATION_FULL; + if (mds_mitigation =3D=3D MDS_MITIGATION_AUTO) { + if (should_mitigate_vuln(X86_BUG_MDS)) + mds_mitigation =3D MDS_MITIGATION_FULL; + else + mds_mitigation =3D MDS_MITIGATION_OFF; + } =20 if (mds_mitigation =3D=3D MDS_MITIGATION_OFF) return; @@ -453,7 +457,7 @@ static void __init mds_select_mitigation(void) =20 static void __init mds_update_mitigation(void) { - if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) + if (!boot_cpu_has_bug(X86_BUG_MDS)) return; =20 /* If TAA, MMIO, or RFDS are being mitigated, MDS gets mitigated too. */ @@ -474,7 +478,7 @@ static void __init mds_apply_mitigation(void) mds_mitigation =3D=3D MDS_MITIGATION_VMWERV) { setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) && - (mds_nosmt || cpu_mitigations_auto_nosmt())) + (mds_nosmt || smt_mitigations =3D=3D SMT_MITIGATIONS_ON)) cpu_smt_disable(false); } } --=20 2.34.1