x86/bugs: Use early_param() for spectre_v2_user

JIRA: https://issues.redhat.com/browse/RHEL-119227

commit 8edb9e7
Author: David Kaplan <david.kaplan@amd.com>
Date:   Mon, 15 Sep 2025 08:47:00 -0500

    x86/bugs: Use early_param() for spectre_v2_user

    Most of the mitigations in bugs.c use early_param() to parse their command
    line options.  Modify spectre_v2_user to use early_param() for consistency.

    Remove spec_v2_user_print_cond() because informing a user about their
    cmdline choice isn't very interesting and the chosen mitigation is already
    printed in spectre_v2_user_update_mitigation().

    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/20250819192200.2003074-2-david.kaplan@amd.com

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

arch/x86/kernel/cpu/bugs.c

@@ -1847,7 +1847,7 @@ enum spectre_v2_mitigation_cmd {
 
 static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init = SPECTRE_V2_CMD_AUTO;
 
-enum spectre_v2_user_cmd {
+enum spectre_v2_user_mitigation_cmd {
 	SPECTRE_V2_USER_CMD_NONE,
 	SPECTRE_V2_USER_CMD_AUTO,
 	SPECTRE_V2_USER_CMD_FORCE,
@@ -1857,6 +1857,9 @@ enum spectre_v2_user_cmd {
 	SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
 };
 
+static enum spectre_v2_user_mitigation_cmd spectre_v2_user_cmd __ro_after_init =
+	IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ? SPECTRE_V2_USER_CMD_AUTO : SPECTRE_V2_USER_CMD_NONE;
+
 static const char * const spectre_v2_user_strings[] = {
 	[SPECTRE_V2_USER_NONE]			= "User space: Vulnerable",
 	[SPECTRE_V2_USER_STRICT]		= "User space: Mitigation: STIBP protection",
@@ -1865,50 +1868,31 @@ static const char * const spectre_v2_user_strings[] = {
 	[SPECTRE_V2_USER_SECCOMP]		= "User space: Mitigation: STIBP via seccomp and prctl",
 };
 
-static const struct {
-	const char			*option;
-	enum spectre_v2_user_cmd	cmd;
-	bool				secure;
-} v2_user_options[] __initconst = {
-	{ "auto",		SPECTRE_V2_USER_CMD_AUTO,		false },
-	{ "off",		SPECTRE_V2_USER_CMD_NONE,		false },
-	{ "on",			SPECTRE_V2_USER_CMD_FORCE,		true  },
-	{ "prctl",		SPECTRE_V2_USER_CMD_PRCTL,		false },
-	{ "prctl,ibpb",		SPECTRE_V2_USER_CMD_PRCTL_IBPB,		false },
-	{ "seccomp",		SPECTRE_V2_USER_CMD_SECCOMP,		false },
-	{ "seccomp,ibpb",	SPECTRE_V2_USER_CMD_SECCOMP_IBPB,	false },
-};
-
-static void __init spec_v2_user_print_cond(const char *reason, bool secure)
-{
-	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
-		pr_info("spectre_v2_user=%s forced on command line.\n", reason);
-}
-
-static enum spectre_v2_user_cmd __init spectre_v2_parse_user_cmdline(void)
+static int __init spectre_v2_user_parse_cmdline(char *str)
 {
-	char arg[20];
-	int ret, i;
-
-	if (!IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2))
-		return SPECTRE_V2_USER_CMD_NONE;
-
-	ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
-				  arg, sizeof(arg));
-	if (ret < 0)
-		return SPECTRE_V2_USER_CMD_AUTO;
+	if (!str)
+		return -EINVAL;
 
-	for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
-		if (match_option(arg, ret, v2_user_options[i].option)) {
-			spec_v2_user_print_cond(v2_user_options[i].option,
-						v2_user_options[i].secure);
-			return v2_user_options[i].cmd;
-		}
-	}
+	if (!strcmp(str, "auto"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_AUTO;
+	else if (!strcmp(str, "off"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_NONE;
+	else if (!strcmp(str, "on"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_FORCE;
+	else if (!strcmp(str, "prctl"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_PRCTL;
+	else if (!strcmp(str, "prctl,ibpb"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_PRCTL_IBPB;
+	else if (!strcmp(str, "seccomp"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_SECCOMP;
+	else if (!strcmp(str, "seccomp,ibpb"))
+		spectre_v2_user_cmd = SPECTRE_V2_USER_CMD_SECCOMP_IBPB;
+	else
+		pr_err("Ignoring unknown spectre_v2_user option (%s).", str);
 
-	pr_err("Unknown user space protection option (%s). Switching to default\n", arg);
-	return SPECTRE_V2_USER_CMD_AUTO;
+	return 0;
 }
+early_param("spectre_v2_user", spectre_v2_user_parse_cmdline);
 
 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
 {
@@ -1920,7 +1904,7 @@ static void __init spectre_v2_user_select_mitigation(void)
 	if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
 		return;
 
-	switch (spectre_v2_parse_user_cmdline()) {
+	switch (spectre_v2_user_cmd) {
 	case SPECTRE_V2_USER_CMD_NONE:
 		return;
 	case SPECTRE_V2_USER_CMD_FORCE: