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Peter Anvin" CC: Subject: [PATCH v5 07/16] x86/bugs: Restructure GDS mitigation Date: Fri, 18 Apr 2025 11:17:12 -0500 Message-ID: <20250418161721.1855190-8-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250418161721.1855190-1-david.kaplan@amd.com> References: <20250418161721.1855190-1-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: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS2PEPF0000343E:EE_|DS0PR12MB8443:EE_ X-MS-Office365-Filtering-Correlation-Id: bbab3d03-f270-42ba-6af5-08dd7e9488d6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|82310400026|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?jas4Qdi8XSbr4eDAx83nqRgOLLkKYjokX1deOzD0VULYHEopfGXPw2WwrR3x?= =?us-ascii?Q?oiT/i7SnXcGRgWmMm0FRxL19Kc8RZ1h6Z9rVI/IOZIHAq/7/7rxeZ0oojQdc?= =?us-ascii?Q?w7B4Eq9ydqokxhoQoCy1qTrlWVXOf2j29dHuqZwZd50OBJImjvly3fhc584E?= =?us-ascii?Q?rxn9I+/wD7NKPcdDjpfD4g2x3NbUeAjDvZ1VK/85jNrJp/4XAeGGQg+HKJ0l?= =?us-ascii?Q?qCSvIlbqKjXau0fxw5b9oggjc35AEGcEzetYKtLHLSyw/mSfnCCP/4TZD5zd?= =?us-ascii?Q?DLQBGeHM3FE5UHg0cL7eTWCo74f7HlvI/CLssQq+QIarQzyROBFxHeKsG4gy?= =?us-ascii?Q?nUyqdaaeulu367I2znw4iukR0cIW5QK2gYJq82ZqEKR+ILOCE8h2B74YSfts?= =?us-ascii?Q?WH7DRXmWjNB1gAFX+i0lIVQN6ARIhrawVJeOBJVY4eRTDmgBYym6evdPGgql?= =?us-ascii?Q?geuXzAv/Cw7wdRWdQsp4+IuTio/YNYXOE3RZkuiRnj5biHgCxgKqrGr0N5ya?= =?us-ascii?Q?8xd0/hKUzvPM0DhrpIBXL4gusZNNlZy278j3yrd1OkUJVBsWTt0e97o93+fR?= =?us-ascii?Q?8Qy83iQ1QS+utraEAWJuF7I9vlX6OaFTcWaLtjuhstQs3WetEoQUVemdJyen?= =?us-ascii?Q?GmKgUkhW7uOofjmgMl5qA8KaTRTxETVRhRmthn/RQPF/dNLlgAjVrr4rEldy?= =?us-ascii?Q?8tx487H6PGZv+qjFk75nysfj74MsHN3FLZRTvyVvT5Swhtpd7RibeT3Xizhu?= =?us-ascii?Q?P2JoIetHpLdOObXfKNwjOfBGbeD9gOt36s1zz9eLd3UNPkJQ+iNh4oe/J37m?= =?us-ascii?Q?wRaQL9WwHW4arZ1o39xH7LkIt5JcSNXlPNwkmoSkjV7Hzn6jtlu02CUbzGAX?= =?us-ascii?Q?OnsCrAMaZkuVrdy3NIC1UAYwXF8i7CLoBFMq7G7O958M6OurswgO21CRqFFU?= =?us-ascii?Q?Bwkpgj6FxjgTpdJm7GMON3/CvWPBJ5wyvIuW1dsY2kcrck8peZ1AAcJT3nXY?= =?us-ascii?Q?UBx1uSauK+41nb2pBLWM6qNdyT/aQmsa98+NY1bAJf+UFweDBVB1Lcctd4bq?= =?us-ascii?Q?XQvOjuuQeBKIMLAo0tAKUdX9Mi9wJ3EurC1AaRfvPQPSApEP0WUhsa0M5BEG?= =?us-ascii?Q?Y4036BCORE6ShdI77r/uWtx2T6KJeZQotL97xHuZYsfyou8wuXRxvzwBhF09?= =?us-ascii?Q?QTDL/6R7VpNk8iURG7KJW87viqjhHrfyB4su6CzRjU/6w6NG0mCT1YkEOFDX?= =?us-ascii?Q?ATtWGXML09N5uL86ko67t3sswumDWOcltTg/ewHLeFhy6Zw/PDPxXwxzZPMo?= =?us-ascii?Q?5OXdAgvsBXasKby/FK+4+/KD5HOePWbn6GIZhqQsZwqO6Y6mwdImqzohTBWk?= =?us-ascii?Q?2T4ZrGDRF7yIlr/woM78qFvWI/+8T95x86QiN+AIbMsiwrSZ5rVoJI9XCAzX?= =?us-ascii?Q?dhI8CZRsYgTmvvOWxXrlU88x48p6uSbzSiKhEEsTho7uWqy8rXdKFAYv61a7?= =?us-ascii?Q?20CEaUVPm+XfjjN7Ql0fgIL+4+u9hN6bGN7z?= 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)(1800799024)(82310400026)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Apr 2025 16:17:37.1652 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bbab3d03-f270-42ba-6af5-08dd7e9488d6 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: DS2PEPF0000343E.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB8443 Content-Type: text/plain; charset="utf-8" Restructure GDS mitigation to use select/apply functions to create consistent vulnerability handling. Define new AUTO mitigation for GDS. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 43 +++++++++++++++++++++++++------------- 1 file changed, 29 insertions(+), 14 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 942db170eb4e..57f9ebf90472 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -76,6 +76,7 @@ static void __init srbds_apply_mitigation(void); static void __init l1d_flush_select_mitigation(void); static void __init srso_select_mitigation(void); static void __init gds_select_mitigation(void); +static void __init gds_apply_mitigation(void); =20 /* The base value of the SPEC_CTRL MSR without task-specific bits set */ u64 x86_spec_ctrl_base; @@ -227,6 +228,7 @@ void __init cpu_select_mitigations(void) mmio_apply_mitigation(); rfds_apply_mitigation(); srbds_apply_mitigation(); + gds_apply_mitigation(); } =20 /* @@ -827,6 +829,7 @@ early_param("l1d_flush", l1d_flush_parse_cmdline); =20 enum gds_mitigations { GDS_MITIGATION_OFF, + GDS_MITIGATION_AUTO, GDS_MITIGATION_UCODE_NEEDED, GDS_MITIGATION_FORCE, GDS_MITIGATION_FULL, @@ -835,7 +838,7 @@ enum gds_mitigations { }; =20 static enum gds_mitigations gds_mitigation __ro_after_init =3D - IS_ENABLED(CONFIG_MITIGATION_GDS) ? GDS_MITIGATION_FULL : GDS_MITIGATION_= OFF; + IS_ENABLED(CONFIG_MITIGATION_GDS) ? GDS_MITIGATION_AUTO : GDS_MITIGATION_= OFF; =20 static const char * const gds_strings[] =3D { [GDS_MITIGATION_OFF] =3D "Vulnerable", @@ -876,6 +879,7 @@ void update_gds_msr(void) case GDS_MITIGATION_FORCE: case GDS_MITIGATION_UCODE_NEEDED: case GDS_MITIGATION_HYPERVISOR: + case GDS_MITIGATION_AUTO: return; } =20 @@ -899,26 +903,21 @@ static void __init gds_select_mitigation(void) =20 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { gds_mitigation =3D GDS_MITIGATION_HYPERVISOR; - goto out; + return; } =20 if (cpu_mitigations_off()) gds_mitigation =3D GDS_MITIGATION_OFF; /* Will verify below that mitigation _can_ be disabled */ =20 + if (gds_mitigation =3D=3D GDS_MITIGATION_AUTO) + gds_mitigation =3D GDS_MITIGATION_FULL; + /* No microcode */ if (!(x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)) { - if (gds_mitigation =3D=3D GDS_MITIGATION_FORCE) { - /* - * This only needs to be done on the boot CPU so do it - * here rather than in update_gds_msr() - */ - setup_clear_cpu_cap(X86_FEATURE_AVX); - pr_warn("Microcode update needed! Disabling AVX as mitigation.\n"); - } else { + if (gds_mitigation !=3D GDS_MITIGATION_FORCE) gds_mitigation =3D GDS_MITIGATION_UCODE_NEEDED; - } - goto out; + return; } =20 /* Microcode has mitigation, use it */ @@ -939,9 +938,25 @@ static void __init gds_select_mitigation(void) */ gds_mitigation =3D GDS_MITIGATION_FULL_LOCKED; } +} + +static void __init gds_apply_mitigation(void) +{ + if (!boot_cpu_has_bug(X86_BUG_GDS)) + return; + + /* Microcode is present */ + if (x86_arch_cap_msr & ARCH_CAP_GDS_CTRL) + update_gds_msr(); + else if (gds_mitigation =3D=3D GDS_MITIGATION_FORCE) { + /* + * This only needs to be done on the boot CPU so do it + * here rather than in update_gds_msr() + */ + setup_clear_cpu_cap(X86_FEATURE_AVX); + pr_warn("Microcode update needed! Disabling AVX as mitigation.\n"); + } =20 - update_gds_msr(); -out: pr_info("%s\n", gds_strings[gds_mitigation]); } =20 --=20 2.34.1