linux-kernel - [PATCH 1/2] x86/microcode: Add microcode= cmdline parsing

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Message-ID: <20250809094206.28028-2-bp@kernel.org>
Date: Sat,  9 Aug 2025 11:42:05 +0200
From: Borislav Petkov <bp@...nel.org>
To: X86 ML <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	"Borislav Petkov (AMD)" <bp@...en8.de>
Subject: [PATCH 1/2] x86/microcode: Add microcode= cmdline parsing

From: "Borislav Petkov (AMD)" <bp@...en8.de>

Add a "microcode=" command line argument after which all options can be
passed in a comma-separated list.

Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 .../admin-guide/kernel-parameters.txt         |  8 +++--
 arch/x86/kernel/cpu/microcode/core.c          | 30 +++++++++++++++----
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55abf494..7c095177da85 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3767,10 +3767,12 @@
 
 	mga=		[HW,DRM]
 
-	microcode.force_minrev=	[X86]
-			Format: <bool>
+	microcode=      [X86] Control the behavior of the microcode loader.
+	                Available options, comma separated:
+
+			force_minrev
 			Enable or disable the microcode minimal revision
-			enforcement for the runtime microcode loader.
+ 			enforcement for the runtime microcode loader.
 
 	mini2440=	[ARM,HW,KNL]
 			Format:[0..2][b][c][t]
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index b92e09a87c69..351a51861f00 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -43,10 +43,9 @@
 #include "internal.h"
 
 static struct microcode_ops *microcode_ops;
-static bool dis_ucode_ldr = false;
+static bool dis_ucode_ldr;
 
-bool force_minrev = IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV);
-module_param(force_minrev, bool, S_IRUSR | S_IWUSR);
+bool force_minrev = false;
 
 /*
  * Synchronization.
@@ -126,13 +125,34 @@ bool __init microcode_loader_disabled(void)
 	return dis_ucode_ldr;
 }
 
+static void early_parse_cmdline(void)
+{
+	char cmd_buf[64] = {};
+	char *s, *p = cmd_buf;
+
+	if (cmdline_find_option(boot_command_line, "microcode", cmd_buf, 64) > 0) {
+		while ((s = strsep(&p, ","))) {
+			if (IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV)) {
+				if (!strcmp("force_minrev", s))
+					force_minrev = true;
+			}
+
+			if (!strcmp(s, "dis_ucode_ldr"))
+				dis_ucode_ldr = true;
+		}
+	}
+
+	/* old, compat option */
+	if (cmdline_find_option_bool(boot_command_line, "dis_ucode_ldr") > 0)
+		dis_ucode_ldr = true;
+}
+
 void __init load_ucode_bsp(void)
 {
 	unsigned int cpuid_1_eax;
 	bool intel = true;
 
-	if (cmdline_find_option_bool(boot_command_line, "dis_ucode_ldr") > 0)
-		dis_ucode_ldr = true;
+	early_parse_cmdline();
 
 	if (microcode_loader_disabled())
 		return;
-- 
2.43.0