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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BN2PEPF00004FBD.mail.protection.outlook.com (10.167.243.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8880.14 via Frontend Transport; Wed, 25 Jun 2025 15:58:19 +0000 Received: from tiny.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Wed, 25 Jun 2025 10:58:16 -0500 From: David Kaplan To: Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , , "H . Peter Anvin" CC: Subject: [PATCH 2/3] x86/bugs: Use IBPB for retbleed if used by SRSO Date: Wed, 25 Jun 2025 10:58:04 -0500 Message-ID: <20250625155805.600376-3-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250625155805.600376-1-david.kaplan@amd.com> References: <20250625155805.600376-1-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: BN2PEPF00004FBD:EE_|DS2PR12MB9774:EE_ X-MS-Office365-Filtering-Correlation-Id: 8fb1923e-988f-44d3-732d-08ddb4011b0c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|82310400026|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?ZIonYULDQNo76oMKYLyWW7qs0iy7l4rQ0ZRrQFzLEcFnk6jeS4Pzew1uOfw6?= =?us-ascii?Q?5PU2NPSsfca78xrKJpqiEBU0YX3Lk3bvBjSpkAb8p8WSE/u9/w1mZ5Oa+N7t?= =?us-ascii?Q?9TbRCsApDFsTfkRHE4Y83EHCtlNNC1u3kPOzaI2rp8vQaT/LlXdytqQsvbfW?= =?us-ascii?Q?IbnVtFbbQJZNjoC0VNSQpVrZo1YB5AhpsLihROv8SzaHhpzEY0rH/QVWCRiK?= =?us-ascii?Q?B1icuMGMddykZ167euCmdrH013Re3p8lEHO9iKDhJdg2HGNj3SO/oxlryBky?= =?us-ascii?Q?5KhYyANGA37PLVkRa8ubpPSW+9saSCB9b8dPNXuSYBwMakEaOCW+M3mGQg2Q?= =?us-ascii?Q?nY6pqcxDngCb7WQQai6pGxUNoyo2wdmagp/NdF5fGiIvfraANbn8qeu6p4LW?= =?us-ascii?Q?7F+mc+8n6irhhkD5bphwbi1Q44MSDqFv7V+RDMSSWICOwFCx5l8/wzLOVF4m?= =?us-ascii?Q?loa3oeIWSvJO7Obz8uUBkvfhzoCdeWxCzo0h3VANql1BkW4fjN/HR6+RYBwn?= =?us-ascii?Q?ojq7+RZIGQgnCcBlZ/wO91UUJbCrtVKyq++oAr8BsRjN2hXxMBNrCo2BgRNC?= =?us-ascii?Q?L39aXWgnjLlJayRBjwJiBzGD01XUkTJF2eooZKaEMYffOU0hPhfbI31GibCo?= =?us-ascii?Q?TTdtRCc5dBfgBgY640sQlNJcCDPx7ilknE3zglyfA1swtIHSQBTJuDVzsE3a?= =?us-ascii?Q?uMheLW9xK4cnwKO+KHxTUc9A8Ltc2OrJyChtEIDIOFD96wUEcanKAh1qbi8t?= =?us-ascii?Q?JD6R2oWOigH914kG0g40rNZE4P5Mc40i/3fvw1/HNy7vdvZBUdwEdwoS1vr5?= =?us-ascii?Q?OvuJhTI1jf77yB8y+PECnA/tvNBaIZiBSWQWKPfhV4MV+4EK+5W5W2tfbaL1?= =?us-ascii?Q?PMFVar7/b5M7fxgq0pZLZaWGume3rnR+nxzvGFIWLGj6A3UVwaLs9dhuVev9?= =?us-ascii?Q?hr2QTy0f8d87dQMKfU+PYRHN44yzg1HjUl9zmTyl0iAKujo/GJmrxY9N+ZoA?= =?us-ascii?Q?mDaHl7hXBWpSYUoAjiEw63XiiS842uvHyG8qHoJ2HMQGwjg8ytF3heLqeNZN?= =?us-ascii?Q?riTo5Om1ECdhc5AmUleA7VIBbyAMWvDvcs++cbV4bLOrA6BeiTNaTWkIp6o1?= =?us-ascii?Q?nBC5apj0DvXJVtP/dLatuDirxVaPEwNy+5+RtD/AsqKKEBdhYgZ3YNJXG/5h?= =?us-ascii?Q?4DoKEfsbXc2xnptIY/WrNeWzN/Vigrn0/Uo2lQqZ6MoPtiYEaFWukXPRLeoi?= =?us-ascii?Q?MKhQLdiA9iqeqmNgHZbfybwzFZGRfbj7xsajlE05f79KeBesNguAcn078LGD?= =?us-ascii?Q?F3RXBrY9RG/iEWfcoFPLdqNo4DIOr/yOMSsQXr7IklCHZn3jsrTD3lazBmkx?= =?us-ascii?Q?2/YwauKM8hACkeRKPd8DrzR+sBkSUiRE+A4lmxxhF53iTF8DFuzaKOAZW10N?= =?us-ascii?Q?0ZMDRN6rW0Ch5TtCPzo5baFy8g1P5dcPzXzB7Hl2682W+X/Tss1Ii9vILRrK?= =?us-ascii?Q?VRz5CbkE0cpLQ/21BnCBiT/fD4CHkeEVcerf?= 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)(376014)(7416014)(1800799024)(82310400026)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Jun 2025 15:58:19.7818 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8fb1923e-988f-44d3-732d-08ddb4011b0c 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: BN2PEPF00004FBD.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9774 Content-Type: text/plain; charset="utf-8" If spec_rstack_overflow=3Dibpb then this mitigates retbleed as well. This is relevant for Zen1 and Zen2 CPUs which are vulnerable to both bugs. Signed-off-by: David Kaplan Reviewed-by: Borislav Petkov (AMD) --- arch/x86/kernel/cpu/bugs.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6c991afb7b78..b26341983230 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1171,6 +1171,21 @@ static enum retbleed_mitigation retbleed_mitigation = __ro_after_init =3D =20 static int __ro_after_init retbleed_nosmt =3D false; =20 +enum srso_mitigation { + SRSO_MITIGATION_NONE, + SRSO_MITIGATION_AUTO, + SRSO_MITIGATION_UCODE_NEEDED, + SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED, + SRSO_MITIGATION_MICROCODE, + SRSO_MITIGATION_NOSMT, + SRSO_MITIGATION_SAFE_RET, + SRSO_MITIGATION_IBPB, + SRSO_MITIGATION_IBPB_ON_VMEXIT, + SRSO_MITIGATION_BP_SPEC_REDUCE, +}; + +static enum srso_mitigation srso_mitigation __ro_after_init =3D SRSO_MITIG= ATION_AUTO; + static int __init retbleed_parse_cmdline(char *str) { if (!str) @@ -1280,6 +1295,10 @@ static void __init retbleed_update_mitigation(void) if (its_mitigation =3D=3D ITS_MITIGATION_RETPOLINE_STUFF) retbleed_mitigation =3D RETBLEED_MITIGATION_STUFF; =20 + /* If SRSO is using IBPB, that works for retbleed too */ + if (srso_mitigation =3D=3D SRSO_MITIGATION_IBPB) + retbleed_mitigation =3D RETBLEED_MITIGATION_IBPB; + if (retbleed_mitigation =3D=3D RETBLEED_MITIGATION_STUFF && !cdt_possible(spectre_v2_enabled)) { pr_err("WARNING: retbleed=3Dstuff depends on retpoline\n"); @@ -2845,19 +2864,6 @@ early_param("l1tf", l1tf_cmdline); #undef pr_fmt #define pr_fmt(fmt) "Speculative Return Stack Overflow: " fmt =20 -enum srso_mitigation { - SRSO_MITIGATION_NONE, - SRSO_MITIGATION_AUTO, - SRSO_MITIGATION_UCODE_NEEDED, - SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED, - SRSO_MITIGATION_MICROCODE, - SRSO_MITIGATION_NOSMT, - SRSO_MITIGATION_SAFE_RET, - SRSO_MITIGATION_IBPB, - SRSO_MITIGATION_IBPB_ON_VMEXIT, - SRSO_MITIGATION_BP_SPEC_REDUCE, -}; - static const char * const srso_strings[] =3D { [SRSO_MITIGATION_NONE] =3D "Vulnerable", [SRSO_MITIGATION_UCODE_NEEDED] =3D "Vulnerable: No microcode", @@ -2870,8 +2876,6 @@ static const char * const srso_strings[] =3D { [SRSO_MITIGATION_BP_SPEC_REDUCE] =3D "Mitigation: Reduced Speculation" }; =20 -static enum srso_mitigation srso_mitigation __ro_after_init =3D SRSO_MITIG= ATION_AUTO; - static int __init srso_parse_cmdline(char *str) { if (!str) --=20 2.34.1