x86/bugs: Use early_param() for spectre_v2

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.

Remove spec_v2_print_cond() as informing the user of the their cmdline
choice isn't interesting.

  [ bp: Zap spectre_v2_check_cmd(). ]

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Link: https://lore.kernel.org/r/20250819192200.2003074-3-david.kaplan@amd.com

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a5072ec6e5c5e5e6f81619ab63b0c32dec240f1c..c348f14c2b5a802cf1d2044bb2a4fa3715673eef 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1845,7 +1845,8 @@ enum spectre_v2_mitigation_cmd {
        SPECTRE_V2_CMD_IBRS,
 };
 
-static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init = SPECTRE_V2_CMD_AUTO;
+static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init =
+       IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ? SPECTRE_V2_CMD_AUTO : SPECTRE_V2_CMD_NONE;
 
 enum spectre_v2_user_mitigation_cmd {
        SPECTRE_V2_USER_CMD_NONE,
@@ -2039,112 +2040,51 @@ static const char * const spectre_v2_strings[] = {
        [SPECTRE_V2_IBRS]                       = "Mitigation: IBRS",
 };
 
-static const struct {
-       const char *option;
-       enum spectre_v2_mitigation_cmd cmd;
-       bool secure;
-} mitigation_options[] __initconst = {
-       { "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 bool nospectre_v2 __ro_after_init;
 
-static void __init spec_v2_print_cond(const char *reason, bool secure)
+static int __init nospectre_v2_parse_cmdline(char *str)
 {
-       if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
-               pr_info("%s selected on command line.\n", reason);
+       nospectre_v2 = true;
+       spectre_v2_cmd = SPECTRE_V2_CMD_NONE;
+       return 0;
 }
+early_param("nospectre_v2", nospectre_v2_parse_cmdline);
 
-static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
+static int __init spectre_v2_parse_cmdline(char *str)
 {
-       enum spectre_v2_mitigation_cmd cmd;
-       char arg[20];
-       int ret, i;
-
-       cmd = 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;
-
-       ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
-       if (ret < 0)
-               return cmd;
-
-       for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
-               if (!match_option(arg, ret, mitigation_options[i].option))
-                       continue;
-               cmd = mitigation_options[i].cmd;
-               break;
-       }
-
-       if (i >= ARRAY_SIZE(mitigation_options)) {
-               pr_err("unknown option (%s). Switching to default mode\n", arg);
-               return cmd;
-       }
-
-       if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
-            cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
-            cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
-            cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
-            cmd == 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;
-       }
-
-       if ((cmd == SPECTRE_V2_CMD_EIBRS ||
-            cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
-            cmd == 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. Switching to AUTO select\n",
-                      mitigation_options[i].option);
-               return SPECTRE_V2_CMD_AUTO;
-       }
-
-       if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
-            cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
-           !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
-               pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
-                      mitigation_options[i].option);
-               return SPECTRE_V2_CMD_AUTO;
-       }
-
-       if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY)) {
-               pr_err("%s selected but not compiled in. Switching to AUTO select\n",
-                      mitigation_options[i].option);
-               return SPECTRE_V2_CMD_AUTO;
-       }
-
-       if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != 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;
-       }
+       if (!str)
+               return -EINVAL;
 
-       if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_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;
-       }
+       if (nospectre_v2)
+               return 0;
 
-       if (cmd == 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;
-       }
+       if (!strcmp(str, "off"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_NONE;
+       else if (!strcmp(str, "on"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_FORCE;
+       else if (!strcmp(str, "retpoline"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_RETPOLINE;
+       else if (!strcmp(str, "retpoline,amd") ||
+                !strcmp(str, "retpoline,lfence"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_RETPOLINE_LFENCE;
+       else if (!strcmp(str, "retpoline,generic"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_RETPOLINE_GENERIC;
+       else if (!strcmp(str, "eibrs"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_EIBRS;
+       else if (!strcmp(str, "eibrs,lfence"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_EIBRS_LFENCE;
+       else if (!strcmp(str, "eibrs,retpoline"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_EIBRS_RETPOLINE;
+       else if (!strcmp(str, "auto"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       else if (!strcmp(str, "ibrs"))
+               spectre_v2_cmd = SPECTRE_V2_CMD_IBRS;
+       else
+               pr_err("Ignoring unknown spectre_v2 option (%s).", str);
 
-       spec_v2_print_cond(mitigation_options[i].option,
-                          mitigation_options[i].secure);
-       return cmd;
+       return 0;
 }
+early_param("spectre_v2", spectre_v2_parse_cmdline);
 
 static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
 {
@@ -2332,7 +2272,50 @@ static void __init bhi_apply_mitigation(void)
 
 static void __init spectre_v2_select_mitigation(void)
 {
-       spectre_v2_cmd = spectre_v2_parse_cmdline();
+       if ((spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
+           !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) {
+               pr_err("RETPOLINE selected but not compiled in. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if ((spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
+           !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
+               pr_err("EIBRS selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if ((spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
+           !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
+               pr_err("LFENCE selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY)) {
+               pr_err("IBRS selected but not compiled in. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
+               pr_err("IBRS selected but not Intel CPU. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) {
+               pr_err("IBRS selected but CPU doesn't have IBRS. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
+
+       if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) {
+               pr_err("IBRS selected but running as XenPV guest. Switching to AUTO select\n");
+               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
+       }
 
        if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
            (spectre_v2_cmd == SPECTRE_V2_CMD_NONE || spectre_v2_cmd == SPECTRE_V2_CMD_AUTO))