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Peter Anvin" CC: Subject: [PATCH 2/3] x86/bugs: Use early_param for spectre_v2 Date: Mon, 11 Aug 2025 09:26:58 -0500 Message-ID: <20250811142659.152248-3-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250811142659.152248-1-david.kaplan@amd.com> References: <20250811142659.152248-1-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: CY4PEPF0000FCBF:EE_|PH7PR12MB7892:EE_ X-MS-Office365-Filtering-Correlation-Id: 1ab028d2-7adb-4c19-4e7f-08ddd8e329a7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700013|1800799024|7416014|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?Wa3e4XEDRc6albx4ntIuEeJgL5bETEvtgoRzvhT+FYufQZHhvWLp8KEXqJPM?= =?us-ascii?Q?6fzV+KjmM+FyzGhVEYBWHofxAzyb4SGncVVrn0HWUKmShBGfz1JSK/Txe3On?= =?us-ascii?Q?PGLcdA8suEoob6XjPCt3iG3UEOoo75K7iBHoRYLJJlTtchA26uMIZJ/oWdEA?= =?us-ascii?Q?+cimqwHfOAIYd4w2SJ9EfOIX5nEWWgVkC6kuxc9Wi1N6ekmvt9uMr0Lwjw3s?= =?us-ascii?Q?xRRRlmpdO2oMaA2ijxZsr8vD92mA/CkQRccMjY/FzdTEQ91NKSEBMvW9o0MG?= =?us-ascii?Q?cRU73UsR4Dr66Lbo08KTxbL6LJV+msdupG68sbMw+ZBQLBm7ls1IR0k3/0gC?= =?us-ascii?Q?Pf5hjaiOQqgvnsP7jvrGQJ5gqUOEpj3x05nbZB+IanzWSTwByMaiwdSbcDMj?= =?us-ascii?Q?98wXVRCvUHPLz8wuj7bBbLWzkBCwzmi7rV/PsVs01cNvyJta6dxQj+cvx8k/?= =?us-ascii?Q?4MXL/liRxxJq2Up6cHMpOuBPCnaFRvU3UPeNs8SvhrUUJSyBqKe/fU/Zc9qz?= =?us-ascii?Q?b6Y27Pk1qJS1q/kvqnEjbh+cWMN8C3GPLLU5frvB2HrZMEpTXPmw2d5KzM6c?= =?us-ascii?Q?OBhGB6yHxSxtorPyRdNXOUZd6XjFgTl2q8Nacw8r/L6O9DcyDN7qzuOB5S20?= =?us-ascii?Q?m93WZ4O0hBrKA+g3A7JR8bJ6nFEcfpUGs2LeXCnththSmUXuV6CM2kmN5rmy?= =?us-ascii?Q?FSKo+0X78PdssD1tHmDB9uItnyp/2/AU6MOp5pRKvprYtYzFygctkmVcEYoq?= =?us-ascii?Q?d13IStR+KGTNy4otd0IFaUJw4rHljt9kyHc8NMBsZ6xQbd0f34NQNKmOktIc?= =?us-ascii?Q?JjqkkhI5Kn4Nhdm9IezphbxMlfDCrukTN9ppPZpGOnm+8V5XqfNeW7n4Y7SZ?= =?us-ascii?Q?ZcCsaFCL9pxK0sBk1Frju1P6Q2qKChhuU2QGHlvcNXPJNgJE06fthtUkPxSp?= =?us-ascii?Q?k8IBfOTWsUddNZd3oXhZWM4+yX72x1y5pnDCYi08JomeaeD3pwY2oC857j5j?= =?us-ascii?Q?MtFZLAgqeGaG4+e93FxLVK++tggEqjfaDRQCUr/GOOF1ivCo5NldHfdYS7Ak?= =?us-ascii?Q?lnbHdxrPrkRjSF8SvaOHPNuq0F1I8GU9es8WzL06YstDmwGG3Z0g9ksQi3Vd?= =?us-ascii?Q?931cH0KNEOYgU++CwGicJpp4+VCemDp2r/dTogX2s1MsQuqTfsSmQE27aeCK?= =?us-ascii?Q?iQSnK53jyfzoDf4vRPg+SAeX4ykpCPAoK8KN6u0Dt3Fq19GVpG8EvKZ/Ketb?= =?us-ascii?Q?IJjxnf7iJECXddpl1EY53gJu/0PbYOgDo7RetrN+mNUYxZXQB5JBgCrXGqVm?= =?us-ascii?Q?qFuw3WwHfpBUxGuD4NBCNZIUCCODvzgMPKPZHjb3PhCcMWD4z2FwulpEskl8?= =?us-ascii?Q?iY9S3W7xKB9kNVXRl//weybHsFRIFM+qmyy0El9RdozDrQff4r7Fi0cg2Mwe?= =?us-ascii?Q?Gn2BBj/Q8MC6leXLORUlJBRetKwCpD/pIJtv6VsC2rShFF/bRQJnUaXl+u86?= =?us-ascii?Q?SUE/+Zpv8Bpb6uB6B5vw0v9RZppXDus/bO7k?= 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)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Aug 2025 14:27:12.3598 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1ab028d2-7adb-4c19-4e7f-08ddd8e329a7 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: CY4PEPF0000FCBF.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7892 Content-Type: text/plain; charset="utf-8" Most of the mitigations in bugs.c use early_param for command line parsing. Rework the spectre_v2 and nospectre_v2 command line options to be consistent with the others. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 151 +++++++++++++++++++------------------ 1 file changed, 78 insertions(+), 73 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6bfe199b9f3e..19a3891953c3 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1827,7 +1827,8 @@ 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; +static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init =3D + IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ? SPECTRE_V2_CMD_AUTO : SPECTRE_= V2_CMD_NONE; =20 enum spectre_v2_user_mitigation_cmd { SPECTRE_V2_USER_CMD_NONE, @@ -2035,112 +2036,118 @@ static const char * const spectre_v2_strings[] = =3D { [SPECTRE_V2_IBRS] =3D "Mitigation: IBRS", }; =20 -static const struct { - const char *option; - enum spectre_v2_mitigation_cmd cmd; - bool secure; -} mitigation_options[] __initconst =3D { - { "off", SPECTRE_V2_CMD_NONE, false }, - { "on", SPECTRE_V2_CMD_FORCE, true }, - { "retpoline", SPECTRE_V2_CMD_RETPOLINE, false }, - { "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, - { "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, - { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false }, - { "eibrs", SPECTRE_V2_CMD_EIBRS, false }, - { "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE, false }, - { "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE, false }, - { "auto", SPECTRE_V2_CMD_AUTO, false }, - { "ibrs", SPECTRE_V2_CMD_IBRS, false }, -}; - static void __init spec_v2_print_cond(const char *reason, bool secure) { if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) !=3D secure) pr_info("%s selected on command line.\n", reason); } =20 -static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) -{ - enum spectre_v2_mitigation_cmd cmd; - char arg[20]; - int ret, i; +static bool nospectre_v2 __ro_after_init; =20 - cmd =3D IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ? SPECTRE_V2_CMD_AUTO := SPECTRE_V2_CMD_NONE; - if (cmdline_find_option_bool(boot_command_line, "nospectre_v2")) - return SPECTRE_V2_CMD_NONE; +static int __init nospectre_v2_parse_cmdline(char *str) +{ + nospectre_v2 =3D true; + spectre_v2_cmd =3D SPECTRE_V2_CMD_NONE; + return 0; +} +early_param("nospectre_v2", nospectre_v2_parse_cmdline); =20 - ret =3D cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(= arg)); - if (ret < 0) - return cmd; +static int __init spectre_v2_parse_cmdline(char *str) +{ + if (!str) + return -EINVAL; =20 - for (i =3D 0; i < ARRAY_SIZE(mitigation_options); i++) { - if (!match_option(arg, ret, mitigation_options[i].option)) - continue; - cmd =3D mitigation_options[i].cmd; - break; - } + if (nospectre_v2) + return 0; =20 - if (i >=3D ARRAY_SIZE(mitigation_options)) { - pr_err("unknown option (%s). Switching to default mode\n", arg); - return cmd; - } + if (!strcmp(str, "off")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_NONE; + else if (!strcmp(str, "on")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_FORCE; + else if (!strcmp(str, "retpoline")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_RETPOLINE; + else if (!strcmp(str, "retpoline,amd") || + !strcmp(str, "retpoline,lfence")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_RETPOLINE_LFENCE; + else if (!strcmp(str, "retpoline,generic")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_RETPOLINE_GENERIC; + else if (!strcmp(str, "eibrs")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_EIBRS; + else if (!strcmp(str, "eibrs,lfence")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_EIBRS_LFENCE; + else if (!strcmp(str, "eibrs,retpoline")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_EIBRS_RETPOLINE; + else if (!strcmp(str, "auto")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; + else if (!strcmp(str, "ibrs")) + spectre_v2_cmd =3D SPECTRE_V2_CMD_IBRS; + else + pr_err("Ignoring unknown spectre_v2 option (%s).", str); =20 - if ((cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE || - cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_LFENCE || - cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_GENERIC || - cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE || - cmd =3D=3D SPECTRE_V2_CMD_EIBRS_RETPOLINE) && + if ((spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_LFENCE || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_GENERIC || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS_RETPOLINE) && !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) { pr_err("%s selected but not compiled in. Switching to AUTO select\n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if ((cmd =3D=3D SPECTRE_V2_CMD_EIBRS || - cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE || - cmd =3D=3D SPECTRE_V2_CMD_EIBRS_RETPOLINE) && + if ((spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS_RETPOLINE) && !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) { pr_err("%s selected but CPU doesn't have Enhanced or Automatic IBRS. Swi= tching to AUTO select\n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if ((cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_LFENCE || - cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE) && + if ((spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_RETPOLINE_LFENCE || + spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_EIBRS_LFENCE) && !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switchin= g to AUTO select\n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if (cmd =3D=3D SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_= ENTRY)) { + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIG= ATION_IBRS_ENTRY)) { pr_err("%s selected but not compiled in. Switching to AUTO select\n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if (cmd =3D=3D SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor !=3D X86_V= ENDOR_INTEL) { + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor= !=3D X86_VENDOR_INTEL) { pr_err("%s selected but not Intel CPU. Switching to AUTO select\n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if (cmd =3D=3D SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) { + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATUR= E_IBRS)) { pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\= n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - if (cmd =3D=3D SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XEN= PV)) { + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_= FEATURE_XENPV)) { pr_err("%s selected but running as XenPV guest. Switching to AUTO select= \n", - mitigation_options[i].option); - return SPECTRE_V2_CMD_AUTO; + str); + spectre_v2_cmd =3D SPECTRE_V2_CMD_AUTO; } =20 - spec_v2_print_cond(mitigation_options[i].option, - mitigation_options[i].secure); - return cmd; + /* Print a warning if forcing an option. AUTO is not forcing. */ + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_AUTO) + return 0; + + if (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_FORCE) + spec_v2_print_cond(str, true); + else + spec_v2_print_cond(str, false); + + return 0; } +early_param("spectre_v2", spectre_v2_parse_cmdline); =20 static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void) { @@ -2328,8 +2335,6 @@ static void __init bhi_apply_mitigation(void) =20 static void __init spectre_v2_select_mitigation(void) { - spectre_v2_cmd =3D spectre_v2_parse_cmdline(); - if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && (spectre_v2_cmd =3D=3D SPECTRE_V2_CMD_NONE || spectre_v2_cmd =3D=3D S= PECTRE_V2_CMD_AUTO)) return; --=20 2.34.1