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Peter Anvin" CC: , Brendan Jackman , Derek Manwaring Subject: [PATCH v4 01/36] x86/bugs: Restructure mds mitigation Date: Mon, 10 Mar 2025 11:39:48 -0500 Message-ID: <20250310164023.779191-2-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250310164023.779191-1-david.kaplan@amd.com> References: <20250310164023.779191-1-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: BL6PEPF00022573:EE_|IA1PR12MB8357:EE_ X-MS-Office365-Filtering-Correlation-Id: 2adae8ff-1017-4fd9-2597-08dd5ff247c9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|7416014|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?oCMt4pGzfAYxn3AH+4+0QAbe2JuWEjzC0BQWj7/qjgsYrGhAV3yyXRi1PLop?= =?us-ascii?Q?Zbe4Y02rmE4cIkzX5fxdM9qyUG7bYRJeKxSADOOPvVjHTYlLge/9PygpgXin?= =?us-ascii?Q?N7S6h8XEp/aTzbSd+GCnv+YVBz7g3JzSK+C9RbVDMA5ixjEdWEJixBxoL7FK?= =?us-ascii?Q?Z4txeueEc/BoTEdJNty3PYmW97BCXUcQXbNxJ14accvXIF+RKjAS4JkxQJ9R?= =?us-ascii?Q?73Kn0K/DpcjLtPFgiwmL+fZp5Xxzdc9Fc3T4tRUF6m3R0Q8B8fAUwJwaQ21J?= =?us-ascii?Q?DFEyK2g88xVTz4XJ+y2VAVZBdu9N+WWFCwixOqLEa89PVMmbjz76jPsKtuLr?= =?us-ascii?Q?ZYupB8FYusn3bKd90BQ6/RnOkMRgkYB82IW9JfIOPK3iUJysm1gfbhBDkqMG?= =?us-ascii?Q?/RdroTBA35cR5ctfA2ayeE8C9QHyYj9BnN0RyBH8d5WbEIm3puO0Gb6z0JEH?= =?us-ascii?Q?FkonlrkJm180amvOcLu6HbkPQ76Uva5/YBQS+2DnkmjTlnxILU3htcEu0kMa?= =?us-ascii?Q?KZpibGiMI7vQUE79Q6STnDDN03ROJ0CnP0+7H8sjaV81XEOJupkloqazOGNZ?= =?us-ascii?Q?A+PAHrVE7bg0rSSw9J7Svxqs4HJmVNQ7320s8MNJULymRPeeM4TmWIOF45gI?= =?us-ascii?Q?hKIXjqSSLdEOaI2HgtsHC/Ua3w+IYU0eP7z27KDb9z8IXFEBkuM2S+zuVozk?= =?us-ascii?Q?L9cFqvAF1nrGS74czWsc5ETX7Z/9GaPIg9fpypZwttX2nZE0fOvO0WnNvKHQ?= =?us-ascii?Q?nhzKKb3kQRmi1/QZOvvzPW6BOClevPAOqJCp1ETFu0jGyM/FLfdsYQjXuXZ3?= =?us-ascii?Q?a/7ZLRmMUspsDY0H4gROa89VR+Vc5oV2OtW/TJIzwrxYxY0IDzr7Oar1xoW/?= =?us-ascii?Q?taIVXvflPDAi2kYCstO6hJOBQEv0eVRGhsGKgPhL/C82h5lxzRPy1Nl7aHNj?= =?us-ascii?Q?gZf59uatYvZ6suMpgWNA1O3cnBwuLKy2oM4anVRftioEaxGYcL3sOZhOTWoi?= =?us-ascii?Q?hKJrBQbIRfhdBB3nmIeSkPTOAvx/pNOzBByrlwrJRjPciBh1T+g2BijFG5tr?= =?us-ascii?Q?NgN+47u3XEwwVFRVkqzEjrzMWG1heAtw61uMx9lNTr/jAYo3Q92RHSOoEdOt?= =?us-ascii?Q?NkGGi4Qnus5V0pjvxc2eRp6spbJQdf3PWDpMw7yGVNoII1N/8MON2poVvpbN?= =?us-ascii?Q?9H4mgGgux/JLHreETHEgbT1AYZDKIzXhuq6gLm/xUJHiQoYAIQgmzt6hUTTE?= =?us-ascii?Q?hY0M2RR9ZOlO/MLbmWQt14HRNT16dd1PK+joXrSxpmWczH/WUdpVkPAe9zl4?= =?us-ascii?Q?87gOoCTSxuiEzM+oDISil94hNtH9tJw9zmSFF6X679nLLZR/+DNGy9drNU4b?= =?us-ascii?Q?QbiJLhID8pHCIxAOWzEGm8WSprF7WWws6VIDv9Oa8GcDuRni8c11ZLFdNbT/?= =?us-ascii?Q?hHMFWQilmLOTLjSSfe4J6n7kiQgtVyD8wxKXRLaDdA6XeyTT4q1MyoZ83bUP?= =?us-ascii?Q?t2/dyLQ57B77yXg=3D?= 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)(1800799024)(36860700013)(7416014)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Mar 2025 16:40:34.7098 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2adae8ff-1017-4fd9-2597-08dd5ff247c9 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: BL6PEPF00022573.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8357 Content-Type: text/plain; charset="utf-8" Restructure mds mitigation selection to use select/update/apply functions to create consistent vulnerability handling. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 55 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 53 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4386aa6c69e1..71da57c4f83b 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -34,6 +34,25 @@ =20 #include "cpu.h" =20 +/* + * Speculation Vulnerability Handling + * + * Each vulnerability is handled with the following functions: + * _select_mitigation() -- Selects a mitigation to use. This shou= ld + * take into account all relevant command line + * options. + * _update_mitigation() -- This is called after all vulnerabilitie= s have + * selected a mitigation, in case the selection + * may want to change based on other choices + * made. This function is optional. + * _apply_mitigation() -- Enable the selected mitigation. + * + * The compile-time mitigation in all cases should be AUTO. An explicit + * command-line option can override AUTO. If no such option is + * provided, _select_mitigation() will override AUTO to the best + * mitigation option. + */ + static void __init spectre_v1_select_mitigation(void); static void __init spectre_v2_select_mitigation(void); static void __init retbleed_select_mitigation(void); @@ -41,6 +60,8 @@ static void __init spectre_v2_user_select_mitigation(void= ); static void __init ssb_select_mitigation(void); static void __init l1tf_select_mitigation(void); static void __init mds_select_mitigation(void); +static void __init mds_update_mitigation(void); +static void __init mds_apply_mitigation(void); static void __init md_clear_update_mitigation(void); static void __init md_clear_select_mitigation(void); static void __init taa_select_mitigation(void); @@ -169,6 +190,7 @@ void __init cpu_select_mitigations(void) spectre_v2_user_select_mitigation(); ssb_select_mitigation(); l1tf_select_mitigation(); + mds_select_mitigation(); md_clear_select_mitigation(); srbds_select_mitigation(); l1d_flush_select_mitigation(); @@ -179,6 +201,14 @@ void __init cpu_select_mitigations(void) */ srso_select_mitigation(); gds_select_mitigation(); + + /* + * After mitigations are selected, some may need to update their + * choices. + */ + mds_update_mitigation(); + + mds_apply_mitigation(); } =20 /* @@ -281,6 +311,9 @@ enum rfds_mitigations { static enum rfds_mitigations rfds_mitigation __ro_after_init =3D IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_AUTO : RFDS_MITIGATI= ON_OFF; =20 +/* Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW. */ +static bool verw_mitigation_selected __ro_after_init; + static void __init mds_select_mitigation(void) { if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) { @@ -291,12 +324,31 @@ static void __init mds_select_mitigation(void) if (mds_mitigation =3D=3D MDS_MITIGATION_AUTO) mds_mitigation =3D MDS_MITIGATION_FULL; =20 + verw_mitigation_selected =3D true; +} + +static void __init mds_update_mitigation(void) +{ + if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) + return; + + /* If TAA, MMIO, or RFDS are being mitigated, MDS gets mitigated too. */ + if (verw_mitigation_selected) + mds_mitigation =3D MDS_MITIGATION_FULL; + if (mds_mitigation =3D=3D MDS_MITIGATION_FULL) { if (!boot_cpu_has(X86_FEATURE_MD_CLEAR)) mds_mitigation =3D MDS_MITIGATION_VMWERV; + } =20 - setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + pr_info("%s\n", mds_strings[mds_mitigation]); +} =20 +static void __init mds_apply_mitigation(void) +{ + if (mds_mitigation =3D=3D MDS_MITIGATION_FULL || + 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())) cpu_smt_disable(false); @@ -599,7 +651,6 @@ static void __init md_clear_update_mitigation(void) =20 static void __init md_clear_select_mitigation(void) { - mds_select_mitigation(); taa_select_mitigation(); mmio_select_mitigation(); rfds_select_mitigation(); --=20 2.34.1