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Peter Anvin" CC: Alexander Graf , Boris Ostrovsky , Subject: [RFC PATCH 10/56] x86/bugs: Reset MDS mitigations Date: Mon, 13 Oct 2025 09:33:58 -0500 Message-ID: <20251013143444.3999-11-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251013143444.3999-1-david.kaplan@amd.com> References: <20251013143444.3999-1-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: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002BA50:EE_|CY8PR12MB7588:EE_ X-MS-Office365-Filtering-Correlation-Id: a61601f5-4cf3-49f5-0c63-08de0a65bf76 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|7416014|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?iqfv9r2fg1cYTqsaROMqkRneMAIRN8uDhpUClayiHEHSYAB59pAYutN5V8DY?= =?us-ascii?Q?W+rXILGzApU8udMsAFdX6gGXVz1LR1UIUtzVbhfLa/DgYbiuXNW0krkGeY/f?= =?us-ascii?Q?t5bT+6zv3cP36VNiDBnUXHZBptys1h2VcSNXpfyjuPCzgRXEC67IYA71O6qf?= =?us-ascii?Q?gYWPzSlKY7Ym51zTwwSm6uK3y9nbX6mNaCQ8kZ2j3XSM4tUUna/b4RsavIRl?= =?us-ascii?Q?fwg1dgDQaURllKFebMLBmRiTLADA6GaJIxWdl3LBHluzU+O6weY3cOoFT4VA?= =?us-ascii?Q?yWShcxuhpJWGRAc014l+fxMwoA9sy9vC9C15MRPg9N5+bxykQuQuqOWHF48P?= =?us-ascii?Q?orAJkylXuQQsZqkiPQSEt8X70fr9AQVbdx93Z23cFkFWbpbgqXmI0Ua/cjvE?= =?us-ascii?Q?6Seo3FEd2EDKhdQY/PbPl5A068bskjecop8fSNQ3oEZG5U/kxxl1iiJTr3Oo?= =?us-ascii?Q?64opzKkv071YGBvdd35XFUf2DFcESoX/aDXPHpnqAgU/pTdrmZTlCONI3sHs?= =?us-ascii?Q?kQ7CbV6fLzlhcbQxjYQBgmJgXr5+/gDixC9053uXzWBfpFDgowQKO3rpM+64?= =?us-ascii?Q?QF//hHv4jXaRkH6kjthWUHmPY/nw5dAgzcdC2T1vdiuzB3zbWi2AH5PivjXX?= =?us-ascii?Q?vOxEXJMMw2W0YZ16OTU/RFcGrXkMv21jl6cfwA0oVRYIzB7ekCpFLhbE91eq?= =?us-ascii?Q?WQGEryKn5MjQ3faJzmd0MnHoTZ8nX7+t4SyKIoWTUumZljmxVLn/5JT5yZDy?= =?us-ascii?Q?udFEJ9vvZoae6PbBc1irhH61yqR7nkbfHXKPIgyTTvysescx7toGydHXQmgT?= =?us-ascii?Q?Wz6Rr2c61RGtMW1rQ3GN2gNY6XFj4kyp/5ocKFNT0EBvsFlUdgcAooQTToCk?= =?us-ascii?Q?bVHK0prrRrDO7y3MTOJNAr8Y/gJqf99tOEIN1PvNEVlE+mN/809E8d/uEDHn?= =?us-ascii?Q?lyiAUmNGCinomrcQQGisBiw0Cz+TI/orefe31f9SZOLYvpMuEokiGJcEvkt0?= =?us-ascii?Q?IGvXfcBPVR3qUPsBHRuIUFMq83Bz97TKMNpQc/NQaF9rpdc+wwWaI5QrXVdf?= =?us-ascii?Q?yD+P6Dm7l5R+OO7y6fN9MbX6FrlJaYa3MygsMbRPfZTAe/+JGaErK+DzflPw?= =?us-ascii?Q?mmQXIWdlPAf2sqirkZRvxnGEpOGGg3IUXaHywiq1skkfcdQIUFzYvgxdHfNY?= =?us-ascii?Q?m65JpbWO1HeZVLyIUmQUgANYJyHPY6O9Z4RSPqfvHDp36URLjKQ+T/3oL5iF?= =?us-ascii?Q?jdGeKYd6HHabyLvXj26rxhD3F5FzAEIB3wMgBCsDkltAj+rH1sFfQe87Biwq?= =?us-ascii?Q?tLEpeFzak3/KOML5AINQur7XmvdtmtvrOyVgQh8asZrooMYd4gebcgmYcrvR?= =?us-ascii?Q?eu4m4ZT4ERP93KIjk898nBvqZBgf5HYcpRA1F6I6orKVkEscIo37yUi30cfC?= =?us-ascii?Q?8cD04nPkYXfBrz+FuSCFAAufmvb2Avm4pJDsV2zFslpyuodTqjzdjjYv8J7M?= =?us-ascii?Q?p6wBEKefE5Z5CyCTXzYqviWcZl86V8Qq8WqF7ffjeduXTmb+vrLEZcsFDTbX?= =?us-ascii?Q?6eyhQLsLjvE8mW+0BhQ=3D?= 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)(36860700013)(1800799024)(7416014)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2025 14:35:25.2691 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a61601f5-4cf3-49f5-0c63-08de0a65bf76 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: SN1PEPF0002BA50.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7588 Content-Type: text/plain; charset="utf-8" Add function to reset MDS mitigations back to their boot-time defaults. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index b61bbeaf82b1..5668a8b8821b 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -554,6 +554,16 @@ static void __init mds_apply_mitigation(void) } } =20 +#ifdef CONFIG_DYNAMIC_MITIGATIONS +static void mds_reset_mitigation(void) +{ + setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + static_branch_disable(&cpu_buf_idle_clear); + mds_mitigation =3D IS_ENABLED(CONFIG_MITIGATION_MDS) ? + MDS_MITIGATION_AUTO : MDS_MITIGATION_OFF; +} +#endif + static int __init mds_cmdline(char *str) { if (!boot_cpu_has_bug(X86_BUG_MDS)) @@ -3891,5 +3901,6 @@ void arch_cpu_reset_mitigations(void) spectre_v2_user_reset_mitigation(); ssb_reset_mitigation(); l1tf_reset_mitigation(); + mds_reset_mitigation(); } #endif --=20 2.34.1