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Message-ID: <20250819192200.2003074-3-david.kaplan@amd.com>
Date: Tue, 19 Aug 2025 14:21:57 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 2/5] 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.
Signed-off-by: David Kaplan <david.kaplan@....com>
---
arch/x86/kernel/cpu/bugs.c | 186 +++++++++++++++++--------------------
1 file changed, 87 insertions(+), 99 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index de78b76ae851..44e0315b58a5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1824,7 +1824,8 @@ 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,
@@ -2021,112 +2022,51 @@ 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)
{
@@ -2312,9 +2252,57 @@ static void __init bhi_apply_mitigation(void)
setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_VMEXIT);
}
+static void __init spectre_v2_check_cmd(void)
+{
+ 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;
+ }
+}
+
static void __init spectre_v2_select_mitigation(void)
{
- spectre_v2_cmd = spectre_v2_parse_cmdline();
+ spectre_v2_check_cmd();
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
(spectre_v2_cmd == SPECTRE_V2_CMD_NONE || spectre_v2_cmd == SPECTRE_V2_CMD_AUTO))
--
2.34.1
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