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Peter Anvin" CC: Subject: [PATCH v5 11/16] x86/bugs: Restructure spectre_v2_user mitigation Date: Fri, 18 Apr 2025 11:17:16 -0500 Message-ID: <20250418161721.1855190-12-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_|IA0PR12MB8696:EE_ X-MS-Office365-Filtering-Correlation-Id: fa3f64fb-2638-471e-7f6b-08dd7e948a90 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700013|1800799024|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?LG/SHL9RMNgSHe3Ez1uLmydIStVAsOup6u8+RrLcNCWmjVyDErccGwf3rAmq?= =?us-ascii?Q?HPv8yhyAKDo7rZmSRGjXvN3ICsMRXRoAIAqBLNW2In8RQF4ZaqaSwvEn2gHv?= =?us-ascii?Q?Yjs9ZJNvSHoBguH9nxGMZ4XRNYLDVGDriwK3ATt2Zi9eQNCABdaGzxiEWBSr?= =?us-ascii?Q?rWTdXpBXX1A0H5yyWVwYN2/eQ7vtkIXIA3wdfk47VyIB7qQ5E19Du0ZB84Na?= =?us-ascii?Q?vbXpwszyEQ0JYocWq/3EAzm1+1FElSKq01wVRHuX9B4aQIgLHv6tj5TmUgC0?= =?us-ascii?Q?ZfHvCcGx18pJ+Fe6IHypL1+d6V7qnKWrz5mkS2waON+g34k7twT+dfRro+h9?= =?us-ascii?Q?E4lZyuyp2sBc0XgF/xRpqpvKJtiwtOoqrByHpMrKm8BMw//7ebB2EY5HoNMx?= =?us-ascii?Q?S3ahmyvOqBpn+sDlQ4i5bd5IFRWHD08DEN59+GTL3PxYYCSl181Vzn3Y/i0N?= =?us-ascii?Q?692HhTuSH4FuarEv+u/r927+2dr4ctXAB+sJrKK5gCjwirtRoej4NqWZmY7w?= =?us-ascii?Q?0d7o6NTXPxuzUhoJP1A60yy2eCfHAMhXeUMrgW3n/rFP8IWNPzmOQ1Qv4+xc?= =?us-ascii?Q?j0S6HwJ/LkXVSLUP3R0ViFKu2TXKcnNAj3SD7+t+cv2fbkckZ49csBAfQYrc?= =?us-ascii?Q?7jYdGIY279IdCxIZioQuU8GRcRky2lRh1Kf/Dp284dr/iY7hVC7DRH4eYKdT?= =?us-ascii?Q?JDnF2oQKWga/mywVfg03kASqOFYcpgDyZbyKlSPaSCmnn44PZo/oi5QDRYm5?= =?us-ascii?Q?1siKk5ZZl+xhaW7CQbEiLwL8WtxKUy2/BbR4sD+dEnrWnhCH/6PZGGkBlEdh?= =?us-ascii?Q?R4qVh/wt74kEvoP7qJpR+fLxG0nJrYXTHa/0tz4nObffZbVKrbg+UKh9eN8r?= =?us-ascii?Q?0lB4pkVkpZLNYWmiF2OE12X5Tc77aL2druyK0JRxBSyJFJdpyjyPPFhPRzX1?= =?us-ascii?Q?3pq2fXYLyCHt8oABEGvC5e7ozsq7+KkRQ4qmKoCJqaKYr1onhY6Im1s0+HSj?= =?us-ascii?Q?LoJcvavGe1PftUZnnzxnCGdE3j5nN9FszRsooz80cDjXv4LzCyuftgHRNW05?= =?us-ascii?Q?XG5xYJq8we2lyprPq0U4HTY4yMs14sGXBJM2trqN8clyg1szSIma1pUykWpN?= =?us-ascii?Q?M3XaYqIARisbZpgYtGTbFOWE1lJf5RcM3qRSrJIC29991YpVChNNel2WOIeO?= =?us-ascii?Q?bu2HgfZkikrBPzFfyaiGj/+ZBProJLK/7x2WN5h/lvJbcZAZ3siCjcNKgcGj?= =?us-ascii?Q?Q3jSjM/2SObgME479KTD0BcfPv4MdYN/vqFo+EHkE/gyxoQOBrLfxNvoePW8?= =?us-ascii?Q?xhOItNOU/3k9nwXjTqm2tYMbvcxrsIa7DW2VD0TEqIYZ55xlgixNuZzDxMDx?= =?us-ascii?Q?/27DUvGqi9bKv/fXFhgs5wQkMm+psToNHo8MI8kFEgktTHz4B7Qx9POdejcr?= =?us-ascii?Q?HFsvU7rw9GfFlDe3detTZETD/JxxC8+03B8ug6NSB7kqo81KE0hZ02KwYAsd?= =?us-ascii?Q?ScwVFTtgwbk6vgJTl/JSDOszhHrrsyuxqiAO?= 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)(36860700013)(1800799024)(376014)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Apr 2025 16:17:40.0626 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fa3f64fb-2638-471e-7f6b-08dd7e948a90 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: IA0PR12MB8696 Content-Type: text/plain; charset="utf-8" Restructure spectre_v2_user to use select/update/apply functions to create consistent vulnerability handling. The IBPB/STIBP choices are first decided based on the spectre_v2_user command line but can be modified by the spectre_v2 command line option as well. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 155 +++++++++++++++++++++---------------- 1 file changed, 89 insertions(+), 66 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 248b6065f4bc..bb20cfb81015 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -60,6 +60,8 @@ static void __init retbleed_select_mitigation(void); static void __init retbleed_update_mitigation(void); static void __init retbleed_apply_mitigation(void); static void __init spectre_v2_user_select_mitigation(void); +static void __init spectre_v2_user_update_mitigation(void); +static void __init spectre_v2_user_apply_mitigation(void); static void __init ssb_select_mitigation(void); static void __init l1tf_select_mitigation(void); static void __init mds_select_mitigation(void); @@ -190,11 +192,6 @@ void __init cpu_select_mitigations(void) spectre_v1_select_mitigation(); spectre_v2_select_mitigation(); retbleed_select_mitigation(); - /* - * spectre_v2_user_select_mitigation() relies on the state set by - * retbleed_select_mitigation(); specifically the STIBP selection is - * forced for UNRET or IBPB. - */ spectre_v2_user_select_mitigation(); ssb_select_mitigation(); l1tf_select_mitigation(); @@ -217,6 +214,11 @@ void __init cpu_select_mitigations(void) * choices. */ retbleed_update_mitigation(); + /* + * spectre_v2_user_update_mitigation() depends on + * retbleed_update_mitigation(). + */ + spectre_v2_user_update_mitigation(); mds_update_mitigation(); taa_update_mitigation(); mmio_update_mitigation(); @@ -224,6 +226,7 @@ void __init cpu_select_mitigations(void) =20 spectre_v1_apply_mitigation(); retbleed_apply_mitigation(); + spectre_v2_user_apply_mitigation(); mds_apply_mitigation(); taa_apply_mitigation(); mmio_apply_mitigation(); @@ -1374,6 +1377,8 @@ enum spectre_v2_mitigation_cmd { SPECTRE_V2_CMD_IBRS, }; =20 +static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init =3D S= PECTRE_V2_CMD_AUTO; + enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_NONE, SPECTRE_V2_USER_CMD_AUTO, @@ -1412,31 +1417,19 @@ static void __init spec_v2_user_print_cond(const ch= ar *reason, bool secure) pr_info("spectre_v2_user=3D%s forced on command line.\n", reason); } =20 -static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd; - static enum spectre_v2_user_cmd __init spectre_v2_parse_user_cmdline(void) { - enum spectre_v2_user_cmd mode; char arg[20]; int ret, i; =20 - mode =3D IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ? - SPECTRE_V2_USER_CMD_AUTO : SPECTRE_V2_USER_CMD_NONE; - - switch (spectre_v2_cmd) { - case SPECTRE_V2_CMD_NONE: + if (cpu_mitigations_off() || !IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2)) return SPECTRE_V2_USER_CMD_NONE; - case SPECTRE_V2_CMD_FORCE: - return SPECTRE_V2_USER_CMD_FORCE; - default: - break; - } =20 ret =3D cmdline_find_option(boot_command_line, "spectre_v2_user", arg, sizeof(arg)); if (ret < 0) - return mode; + return SPECTRE_V2_USER_CMD_AUTO; =20 for (i =3D 0; i < ARRAY_SIZE(v2_user_options); i++) { if (match_option(arg, ret, v2_user_options[i].option)) { @@ -1447,7 +1440,7 @@ spectre_v2_parse_user_cmdline(void) } =20 pr_err("Unknown user space protection option (%s). Switching to default\n= ", arg); - return mode; + return SPECTRE_V2_USER_CMD_AUTO; } =20 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode) @@ -1458,7 +1451,6 @@ static inline bool spectre_v2_in_ibrs_mode(enum spect= re_v2_mitigation mode) static void __init spectre_v2_user_select_mitigation(void) { - enum spectre_v2_user_mitigation mode =3D SPECTRE_V2_USER_NONE; enum spectre_v2_user_cmd cmd; =20 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP)) @@ -1467,48 +1459,65 @@ spectre_v2_user_select_mitigation(void) cmd =3D spectre_v2_parse_user_cmdline(); switch (cmd) { case SPECTRE_V2_USER_CMD_NONE: - goto set_mode; + return; case SPECTRE_V2_USER_CMD_FORCE: - mode =3D SPECTRE_V2_USER_STRICT; + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_STRICT; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_STRICT; break; case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_PRCTL: + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_PRCTL; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_PRCTL; + break; case SPECTRE_V2_USER_CMD_PRCTL_IBPB: - mode =3D SPECTRE_V2_USER_PRCTL; + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_STRICT; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_PRCTL; break; case SPECTRE_V2_USER_CMD_SECCOMP: + if (IS_ENABLED(CONFIG_SECCOMP)) + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_SECCOMP; + else + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_PRCTL; + spectre_v2_user_stibp =3D spectre_v2_user_ibpb; + break; case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_STRICT; if (IS_ENABLED(CONFIG_SECCOMP)) - mode =3D SPECTRE_V2_USER_SECCOMP; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_SECCOMP; else - mode =3D SPECTRE_V2_USER_PRCTL; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_PRCTL; break; } =20 - /* Initialize Indirect Branch Prediction Barrier */ - if (boot_cpu_has(X86_FEATURE_IBPB)) { - static_branch_enable(&switch_vcpu_ibpb); + /* + * At this point, an STIBP mode other than "off" has been set. + * If STIBP support is not being forced, check if STIBP always-on + * is preferred. + */ + if ((spectre_v2_user_stibp =3D=3D SPECTRE_V2_USER_PRCTL || + spectre_v2_user_stibp =3D=3D SPECTRE_V2_USER_SECCOMP) && + boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) + spectre_v2_user_stibp =3D SPECTRE_V2_USER_STRICT_PREFERRED; =20 - spectre_v2_user_ibpb =3D mode; - switch (cmd) { - case SPECTRE_V2_USER_CMD_NONE: - break; - case SPECTRE_V2_USER_CMD_FORCE: - case SPECTRE_V2_USER_CMD_PRCTL_IBPB: - case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: - static_branch_enable(&switch_mm_always_ibpb); - spectre_v2_user_ibpb =3D SPECTRE_V2_USER_STRICT; - break; - case SPECTRE_V2_USER_CMD_PRCTL: - case SPECTRE_V2_USER_CMD_AUTO: - case SPECTRE_V2_USER_CMD_SECCOMP: - static_branch_enable(&switch_mm_cond_ibpb); - break; - } + if (!boot_cpu_has(X86_FEATURE_IBPB)) + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_NONE; =20 - pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", - static_key_enabled(&switch_mm_always_ibpb) ? - "always-on" : "conditional"); + if (!boot_cpu_has(X86_FEATURE_STIBP)) + spectre_v2_user_stibp =3D SPECTRE_V2_USER_NONE; +} + +static void __init spectre_v2_user_update_mitigation(void) +{ + if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP)) + return; + + /* The spectre_v2 cmd line can override spectre_v2_user options */ + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_NONE) { + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_NONE; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_NONE; + } else if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_FORCE) { + spectre_v2_user_ibpb =3D SPECTRE_V2_USER_STRICT; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_STRICT; } =20 /* @@ -1526,30 +1535,44 @@ spectre_v2_user_select_mitigation(void) if (!boot_cpu_has(X86_FEATURE_STIBP) || !cpu_smt_possible() || (spectre_v2_in_eibrs_mode(spectre_v2_enabled) && - !boot_cpu_has(X86_FEATURE_AUTOIBRS))) + !boot_cpu_has(X86_FEATURE_AUTOIBRS))) { + spectre_v2_user_stibp =3D SPECTRE_V2_USER_NONE; return; + } =20 - /* - * At this point, an STIBP mode other than "off" has been set. - * If STIBP support is not being forced, check if STIBP always-on - * is preferred. - */ - if (mode !=3D SPECTRE_V2_USER_STRICT && - boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) - mode =3D SPECTRE_V2_USER_STRICT_PREFERRED; - - if (retbleed_mitigation =3D=3D RETBLEED_MITIGATION_UNRET || - retbleed_mitigation =3D=3D RETBLEED_MITIGATION_IBPB) { - if (mode !=3D SPECTRE_V2_USER_STRICT && - mode !=3D SPECTRE_V2_USER_STRICT_PREFERRED) + if (spectre_v2_user_stibp !=3D SPECTRE_V2_USER_NONE && + (retbleed_mitigation =3D=3D RETBLEED_MITIGATION_UNRET || + retbleed_mitigation =3D=3D RETBLEED_MITIGATION_IBPB)) { + if (spectre_v2_user_stibp !=3D SPECTRE_V2_USER_STRICT && + spectre_v2_user_stibp !=3D SPECTRE_V2_USER_STRICT_PREFERRED) pr_info("Selecting STIBP always-on mode to complement retbleed mitigati= on\n"); - mode =3D SPECTRE_V2_USER_STRICT_PREFERRED; + spectre_v2_user_stibp =3D SPECTRE_V2_USER_STRICT_PREFERRED; } + pr_info("%s\n", spectre_v2_user_strings[spectre_v2_user_stibp]); +} =20 - spectre_v2_user_stibp =3D mode; +static void __init spectre_v2_user_apply_mitigation(void) +{ + /* Initialize Indirect Branch Prediction Barrier */ + if (spectre_v2_user_ibpb !=3D SPECTRE_V2_USER_NONE) { + static_branch_enable(&switch_vcpu_ibpb); =20 -set_mode: - pr_info("%s\n", spectre_v2_user_strings[mode]); + switch (spectre_v2_user_ibpb) { + case SPECTRE_V2_USER_STRICT: + static_branch_enable(&switch_mm_always_ibpb); + break; + case SPECTRE_V2_USER_PRCTL: + case SPECTRE_V2_USER_SECCOMP: + static_branch_enable(&switch_mm_cond_ibpb); + break; + default: + break; + } + + pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", + static_key_enabled(&switch_mm_always_ibpb) ? + "always-on" : "conditional"); + } } =20 static const char * const spectre_v2_strings[] =3D { --=20 2.34.1