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Peter Anvin" CC: Subject: [PATCH v5 05/20] x86/bugs: Add attack vector controls for MDS Date: Fri, 9 May 2025 11:28:24 -0500 Message-ID: <20250509162839.3057217-6-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250509162839.3057217-1-david.kaplan@amd.com> References: <20250509162839.3057217-1-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: BN3PEPF0000B074:EE_|SA0PR12MB7479:EE_ X-MS-Office365-Filtering-Correlation-Id: 2e84c552-db70-410d-3e33-08dd8f169651 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|36860700013|376014|1800799024|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?wgqIF1sHCXrs9JSlWpBMv8MWAEWozzw8o1OiwHXBMnmtqUgjRBiS9XAqg7g9?= =?us-ascii?Q?FBX5SHeSUimdUQ2qR7Q4FR8g1nXdDQ25/gJOgV+Hw+VIWcN/LlKa2xc/8iKU?= =?us-ascii?Q?gUA8asxkom7cBu3myQS7dEJdIp3CyI/YqGA1R4S5EEo3mBUpsKseIhF1mnJE?= =?us-ascii?Q?kMFXs2PuOnhArIx3+PsJGAy+g7vgzI+aMd6Ll59NbEn9S/DAhy4TNHs8WXTJ?= =?us-ascii?Q?yvJcP86v+EP/P1WWLinhsxg1XQzmGC3wnosvLGYnIB0Pj/4ibZ8NrVH+NqCK?= =?us-ascii?Q?GdXs3wKvFCLbNLPxnssSM1/Fi11NrBl9xysw+Zw2SFOP5y5suTDw2brFAEHU?= =?us-ascii?Q?Y6FIcxe4nBazyM4rBk08mgCDS5BJg/ZFoywraqMH//veFDluxV7hnq0SQBzM?= =?us-ascii?Q?ICdVab+MoUNhOpjAcgdsAp/S2p/NZ8fW4WIZHl4Bywaguc3w/NzpCAY0RuoR?= =?us-ascii?Q?MNj5emhL95UEx6xs6pSylbCZ0Ua37BJSjHfbe3m/auJAvh+/45VFKlp/rhyG?= =?us-ascii?Q?BgvllNzMNHIG0sdQ+ygzmVH2oyTF3349klIIEbgoWnaKyKwkGmdJb7kWP3HK?= =?us-ascii?Q?+drKxdUyAScYAaNe6bovzWgU8x4lAnuGhB7KVtewwAi173otzzMc1KOw2Od+?= =?us-ascii?Q?ymBeoM2RvkDqZ4ysJRML0uurDkBL5se/DlteGArTvOd0Jbg96twNvKYI/Hs+?= =?us-ascii?Q?SfHX4k00M9Ix9vdcyF95HL9bpg9yL8FYXZegxZaD5iAdAQUnZ0R85Wk6e0gD?= =?us-ascii?Q?v5o/ctbyk47U7zgZHQbDzoLwmBxSahOunb4EBgrETv/jMzY0ht/LSnrtjEmK?= =?us-ascii?Q?/sg8VwuWcmhffwCtkSWyUzD62zVpv9h3Dm32wAEeS3/Ct+nlIXGMyAvgrsjO?= =?us-ascii?Q?jZHSBcq6QU6T7a+kn4wdA+Fh7kWTjPynOto0rTswo9K3ZmEWKJHocGsilEGQ?= =?us-ascii?Q?No+SStDHXcEy0tccZRlshR4eSmX29N5OMSQEVufvj93hEnXKuYHjQRDyuCM6?= =?us-ascii?Q?Voe4m0azLu4z7MVfYYr744RQU1u/PJafruQe8JIjNTNB3zTUaDRm2CN2A+ZE?= =?us-ascii?Q?34UQtwrDQsC/SKG7M2oXLo3f60ImAUfRWdwPpiQpUMfGqFfPBnPC/GIo2YHl?= =?us-ascii?Q?ciIUM9tofaWPYYRCCVlrKFyqsvLRMt1rkQyJ6DJwZkBLD/NlgwmG5tYk26DA?= =?us-ascii?Q?6IZbwd7wcYGLTZhyC1zcbst4V+TNlmDpyayZw/zxScEfoitCZSH0Uu53T+ZT?= =?us-ascii?Q?f5z5LQsfX8pXcP8DJEZsitF8EOCW1YqVTSwmPFPIRgN+27Wo0A/Dd4vMNZtb?= =?us-ascii?Q?SyR9o83J7QcF2fe3e98tZVYLzL+8Ajqf1FirRW80NJOanexBe32DmHkxjWf9?= =?us-ascii?Q?pcvPfmxl1FrRmoVzEc14zaBVprSUci3cc0kU6CwHvyadxghs6BCmm/9X5uoJ?= =?us-ascii?Q?ZclUgz2IY5/vrPJnC5PToYA1yudDArxoy+w4EqABE9NopGX6WMFZZ1VvqbcP?= =?us-ascii?Q?T6b138S3l5810WYgpaufl2yNNXWJQ7R0hNgF?= 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)(36860700013)(376014)(1800799024)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 May 2025 16:28:53.0010 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2e84c552-db70-410d-3e33-08dd8f169651 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: BN3PEPF0000B074.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB7479 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 3dce7c3126ea..97d152c33e9e 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -419,13 +419,17 @@ 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; @@ -435,7 +439,7 @@ 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. */ @@ -456,7 +460,7 @@ 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