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Peter Anvin" CC: Alexander Graf , Boris Ostrovsky , Subject: [RFC PATCH 14/56] x86/bugs: Reset GDS mitigations Date: Mon, 13 Oct 2025 09:34:02 -0500 Message-ID: <20251013143444.3999-15-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_|CY8PR12MB7292:EE_ X-MS-Office365-Filtering-Correlation-Id: 73fe5333-decc-4f2d-3f97-08de0a65c116 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|376014|7416014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?UWZZSN2zW4VdrYu8ZUErpfjZsS9U7UiM98OY5bx2dOKZU5oo3bFEvU/Iue30?= =?us-ascii?Q?4Ak/NmxNOUdpEBlIGEozADGl8u9lNFlujKdzUlcWhbCIaHj08/iLBUNTvxX3?= =?us-ascii?Q?q5idvdjFqxxdR47iUSG6ZzuHzujAjkukJTg1EDffllXoy+Ntp/3N06KITPR7?= =?us-ascii?Q?DSl5ec9o4X8IU+jNl01yCGS8s1qMPZwZxPbQIORKI/f7iRmjOLnVk2H5BwHw?= =?us-ascii?Q?3BxwIwvHS1EXKxrC1IbcY7OR8yJLUamABaMSaoAQc5U6piFHo/RFiXnX1/9m?= =?us-ascii?Q?xsff0Jvnys3/vK0nbdcQq6wbMZVm399dWmOQAr7znDq2aR7g90IPhOZjuMw9?= =?us-ascii?Q?vDn+/wPyghe/0zQ3g6fxBBvKQdjlzG03ZgKr4FESbHxLZYBtYuX8rSNAnz2V?= =?us-ascii?Q?z06dQukNIe5rwv+Q5C420JQ3u3LX08Jo7Ah86f6A/Mhj0IfSUx2Wrf/Abe71?= =?us-ascii?Q?jENlC3NKlacw5814DbKZMSx9GuES342k9vi0S/YddTBiUFH7AP9wT/pZFShm?= =?us-ascii?Q?YWnlp6RT6SKkEf0ub53ZbMJoqS5xXfGZzDa9Ow0HFdJ043eVzqJwz2ThLxGs?= =?us-ascii?Q?KxOVgDsjcKsh/O5Z/FbEjslH9wQ8VjC+/FZyb1xce08XxEZaKONsiIJNVa6X?= =?us-ascii?Q?DSZxtbsAKOYPT0WiR+7+X2YzYofsJqy8uRJwMIl9DGYa+DQJGhjzC97aIaNf?= =?us-ascii?Q?3OyuGx9EtZ06jsVSgctLsh/ydQ+cXCN1NbGzA8mfgtxKE2u0lofUhc06XVHD?= =?us-ascii?Q?I9zwjV1/d3ZHv3BMssVt1iHZWdnXPBXP711ppHaio4AK8mT518KsSjm9PSfu?= =?us-ascii?Q?6YGSWXWblGWGXt4EBCrGDEHohP62Og7ZVMIALe47U6hFbvYmGdB8acixJI9y?= =?us-ascii?Q?6Hn9PRgCBCB1S2/aZcD20FEcRHOrQYfE3ZMMcweaBRYoixoSELV1Eb62jzCd?= =?us-ascii?Q?crDTnhuL8O4xHefggLUuK/bk5s6MCdD4syvVs0NjGWXebAgjdcx7pzX9/36J?= =?us-ascii?Q?6bEmQntNifBulLUOEcZuKB2UGYOuy0/d8DBy00XAinns0v5HNhjkiJsNIBEs?= =?us-ascii?Q?q7n6NZi5ceKSAUatHvRssY+FNUH8ms5SiUSRYDh2FhaQ8HffXDpvCmIFwmNz?= =?us-ascii?Q?CiM1bc2GV47WFVy++7hboEK+/TVu0blsaKLM12MJAryz++2AmPcUfdfheQ8L?= =?us-ascii?Q?cx1ofKN5XiO5ARP/8ctyAXFHnZoa6sHv8ancwgwE+JEBdvjqD+EkH7JKSO50?= =?us-ascii?Q?vM5OsGc+8u9vUe28oiJiXa5mIs+oBhQMq1eUNB3/TlmErVu7S7t3JZDo7gPU?= =?us-ascii?Q?1al/yrKLndPWNJ1OjY+HOFYEd+BaLFlCK/cH8DO6so2rbpy0/oCrgqBOU1OY?= =?us-ascii?Q?B2b2URpBNvCzljVC/gz9Ovq/ZujDIapRwkFTtimiL3jRHcLknloRSPIgWMt0?= =?us-ascii?Q?jy3rWJf5FvKXSkLkBp+bdyNmn+IRi7Lr6plDRJ/xYukIVROE7XAuj0yfwCf3?= =?us-ascii?Q?0RHkYcI3TZmFGGcY1tw5T9KiTgKqHdKv8o348MV68oEEyC2SluaNEOi6g4zN?= =?us-ascii?Q?sPdpVvZLJylhYCuDJ2k=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)(1800799024)(36860700013)(376014)(7416014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2025 14:35:27.9966 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 73fe5333-decc-4f2d-3f97-08de0a65c116 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: CY8PR12MB7292 Content-Type: text/plain; charset="utf-8" Add function to reset GDS mitigations back to their boot-time defaults. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 112553058ccc..e765ac0b9240 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1182,6 +1182,18 @@ static void __init gds_apply_mitigation(void) pr_info("%s\n", gds_strings[gds_mitigation]); } =20 +#ifdef CONFIG_DYNAMIC_MITIGATIONS +static void gds_reset_mitigation(void) +{ + /* To cause the MSR bit to be cleared. */ + gds_mitigation =3D GDS_MITIGATION_OFF; + if (x86_arch_cap_msr & ARCH_CAP_GDS_CTRL) + update_gds_msr(); + gds_mitigation =3D IS_ENABLED(CONFIG_MITIGATION_GDS) ? + GDS_MITIGATION_AUTO : GDS_MITIGATION_OFF; +} +#endif + static int __init gds_parse_cmdline(char *str) { if (!str) @@ -3941,5 +3953,6 @@ void arch_cpu_reset_mitigations(void) mmio_reset_mitigation(); srbds_reset_mitigation(); srso_reset_mitigation(); + gds_reset_mitigation(); } #endif --=20 2.34.1