linux-kernel - [RFC PATCH 51/56] cpu: Parse string of mitigation options

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Message-ID: <20251013143444.3999-52-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:39 -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: Alexander Graf <graf@...zon.com>, Boris Ostrovsky
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 51/56] cpu: Parse string of mitigation options

Support runtime parsing of a cmdline-like string of mitigation options.
The global 'mitigations' parameter is processed in generic code and all
other parsing is done via the arch-specific function.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 include/linux/cpu.h |  4 ++++
 kernel/cpu.c        | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 3da629a76a49..6f69344465f1 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -210,6 +210,10 @@ enum smt_mitigations {
 
 void cpu_reset_mitigations(void);
 void arch_cpu_reset_mitigations(void);
+bool cpu_is_mitigation_opt(char *param);
+bool arch_is_mitigation_opt(char *param);
+int cpu_parse_mitigation_options(const char *str);
+int arch_parse_mitigation_opt(char *param, char *val);
 
 #ifdef CONFIG_CPU_MITIGATIONS
 extern bool cpu_mitigations_off(void);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 33289405af30..942a200398c9 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -3343,4 +3343,36 @@ void cpu_reset_mitigations(void)
 	attack_vectors[CPU_MITIGATE_GUEST_GUEST] = IS_ENABLED(CONFIG_KVM);
 	arch_cpu_reset_mitigations();
 }
+
+int __weak arch_parse_mitigation_opt(char *param, char *val) { return 0; }
+bool __weak arch_is_mitigation_opt(char *param) { return false; }
+
+bool cpu_is_mitigation_opt(char *param)
+{
+	if (parameq(param, "mitigations"))
+		return true;
+	else
+		return arch_is_mitigation_opt(param);
+}
+
+static int __cpu_parse_mitigation_options(char *param, char *val,
+		const char *unused, void *arg)
+{
+	if (parameq(param, "mitigations"))
+		return mitigations_parse_cmdline(val);
+	else
+		return arch_parse_mitigation_opt(param, val);
+}
+
+int cpu_parse_mitigation_options(const char *str)
+{
+	char *tmpstr;
+
+	/* Copy the provided string because parse_args will mangle it. */
+	tmpstr = kstrdup(str, GFP_KERNEL);
+	parse_args("dynamic mitigations", tmpstr, NULL, 0, 0, 0, NULL,
+			__cpu_parse_mitigation_options);
+	kfree(tmpstr);
+	return 0;
+}
 #endif
-- 
2.34.1