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Peter Anvin" CC: Subject: [PATCH v6 12/21] x86/bugs: Add attack vector controls for retbleed Date: Mon, 7 Jul 2025 13:33:07 -0500 Message-ID: <20250707183316.1349127-13-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250707183316.1349127-1-david.kaplan@amd.com> References: <20250707183316.1349127-1-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: MWH0EPF000989E9:EE_|BL4PR12MB9479:EE_ X-MS-Office365-Filtering-Correlation-Id: b38d3ed9-836b-4ea4-3dca-08ddbd84cb9b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700013|7416014|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?65h7XrRX+EI/BNStCBhtRrrD9vAMX1A1nq8KrzenoYH0RyKkq6n7kKwyQY9F?= =?us-ascii?Q?v9BbWffMDfl0cbd5WptZsY9hCciGjGnmjnIkI5y2L2mKgOoONM35YkuCxVvb?= =?us-ascii?Q?peha3PzXTrAQR7Wq/gJYw/Y2V58pYI/86Xv0hbuKVKYJptmwih974/wvpNB9?= =?us-ascii?Q?1U7g/2umQdF/ZgzQ+WhgQSkU9gcmflFh3hWXM8/vhcXa8GCzqSdzOJSaJxoO?= =?us-ascii?Q?eRUPylSy+0mzdSOEGUU9hzWDj17HSCGK4AESFaFSYxWavom0cS4GXO/Ozei0?= =?us-ascii?Q?FKcm8om+khcuPwCRvz6ORSM8V9q5z35MFniIZumGM9rmh/IpYwTXrAX7KtKd?= =?us-ascii?Q?GF6usAQhaWGhGxVIW6wmFejkHVDUiJnxgsHZhgaeSVFWk9MHe2btcCwG9dLR?= =?us-ascii?Q?G0LW0pqTc3dahVyaS6C4kucE67TH3C7LEZagahC/4VF0R2VDeqttmpjDNVER?= =?us-ascii?Q?GC1QacgXjD8xQkdq8wp8CkE2dXZEldR4+WKeHondaRf3voqtGumTFUf1tXlr?= =?us-ascii?Q?XReOus4jekyLPk9OY+TNaDnS+TGWaQDveTGeipfm8eKlMVDZZuXlrWNsPNEY?= =?us-ascii?Q?lXQCWNch2iaIIPsqVXv21cp/m6npYoQMCQhS8to4/aieaw+r0jc5cPMqKJt6?= =?us-ascii?Q?kPWu+EjBBGvSZQLfKqnbDpPBGR6lQOWuLrMAxaWPl3tsuq+cI0VGwCvSqGh5?= =?us-ascii?Q?dR3i8NCAP9qynnTkXbxFbnTcwRYEH0zJ0qPVYcxJgA4CO9irRm6DzdAkVPDP?= =?us-ascii?Q?4d2iJShy4hKf0pgqGpmw+0tuCLvjcqTiZncbAdvXdzdVJ0VOzgfu1KsmZyAX?= =?us-ascii?Q?a0l8kSPtciamKwmu5wxKbx81SESu2fJw0kUOU9HOhoIhBriSx5DbeO2pVKM6?= =?us-ascii?Q?SvOPJDsOk/NXxtzkA2eBb8K+Bo5UuZ9mFf1VJBnafV93pyBjZbtqbEZkTQbl?= =?us-ascii?Q?uTbt4lF90fVDL5QiNPX1AOFvJjhlRQcCQD87TTrHMgYz57a+w1xiGa6WH903?= =?us-ascii?Q?5oivae8prOlNeCUop87Gp7J/hIrs6f2hvdY/gC9Dt0UfLz9Kc252q5Pw3S2/?= =?us-ascii?Q?1zp+4WvylBSnzGSM6U16Eg/eqWDxufsgrHZNeGq52NimhnnMgjcr46RT049H?= =?us-ascii?Q?p1cCnKq16izXZCkxsmhVzVzMDR3QB93Zcsdj7+JJPDypqfM7n74/l2ABTAj2?= =?us-ascii?Q?g9lnXWK8p8cKtcQJtOPfmJtaEcSwH6c8bB2qwivvpCAnAKGpellP1Ub62jI0?= =?us-ascii?Q?5Cek3HCEabGbXNxsObYpwZQMWahktvFIzjqR9mhs/kf9pzrXMdvXGgf2U3y/?= =?us-ascii?Q?+g9hcp5G4fXQeGuBEJ1DkCieEOK7fofDj0awlYRf1wAfytef+CDq3QXHi/g0?= =?us-ascii?Q?RSIf61dz2YVFsFBfg2vxlGpMABPWYs5UvKH+3bbMm7mGt/QR1k31H4FP93eP?= =?us-ascii?Q?9MKAAzhhOLpEsZfuRLYjnJU7mu4JHhH1ElwS/5cWN47N1v+/XzJjsTNebv5C?= =?us-ascii?Q?zLsT+oiKUOGz/S+jyckjH3GWnuRZ604vpv3t?= 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)(82310400026)(1800799024)(36860700013)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2025 18:33:40.4428 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b38d3ed9-836b-4ea4-3dca-08ddbd84cb9b 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: MWH0EPF000989E9.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL4PR12MB9479 Content-Type: text/plain; charset="utf-8" Use attack vector controls to determine if retbleed mitigation is required. Disable SMT if cross-thread protection is desired and STIBP is not available. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index f4b3d879ba38..1e2dab9be7db 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1309,7 +1309,7 @@ early_param("retbleed", retbleed_parse_cmdline); =20 static void __init retbleed_select_mitigation(void) { - if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) { + if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) { retbleed_mitigation =3D RETBLEED_MITIGATION_NONE; return; } @@ -1346,6 +1346,11 @@ static void __init retbleed_select_mitigation(void) if (retbleed_mitigation !=3D RETBLEED_MITIGATION_AUTO) return; =20 + if (!should_mitigate_vuln(X86_BUG_RETBLEED)) { + retbleed_mitigation =3D RETBLEED_MITIGATION_NONE; + return; + } + /* Intel mitigation selected in retbleed_update_mitigation() */ if (boot_cpu_data.x86_vendor =3D=3D X86_VENDOR_AMD || boot_cpu_data.x86_vendor =3D=3D X86_VENDOR_HYGON) { @@ -1369,7 +1374,7 @@ static void __init retbleed_select_mitigation(void) =20 static void __init retbleed_update_mitigation(void) { - if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) + if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) return; =20 /* ITS can also enable stuffing */ @@ -1464,7 +1469,7 @@ static void __init retbleed_apply_mitigation(void) } =20 if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) && - (retbleed_nosmt || cpu_mitigations_auto_nosmt())) + (retbleed_nosmt || smt_mitigations =3D=3D SMT_MITIGATIONS_ON)) cpu_smt_disable(false); } =20 --=20 2.34.1