x86/microcode: Add microcode= cmdline parsing

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@alien8.de>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
Link: https://lore.kernel.org/20250820135043.19048-2-bp@kernel.org

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55a..9e3bbce 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3767,8 +3767,12 @@
 
        mga=            [HW,DRM]
 
-       microcode.force_minrev= [X86]
-                       Format: <bool>
+       microcode=      [X86] Control the behavior of the microcode loader.
+                       Available options, comma separated:
+
+                       dis_ucode_ldr: disable the microcode loader
+
+                       force_minrev:
                        Enable or disable the microcode minimal revision
                        enforcement for the runtime microcode loader.
 

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 58d890f..aa250d9 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1340,7 +1340,7 @@ config MICROCODE_LATE_LOADING
          use this at your own risk. Late loading taints the kernel unless the
          microcode header indicates that it is safe for late loading via the
          minimal revision check. This minimal revision check can be enforced on
-         the kernel command line with "microcode.minrev=Y".
+         the kernel command line with "microcode=force_minrev".
 
 config MICROCODE_LATE_FORCE_MINREV
        bool "Enforce late microcode loading minimal revision check"
@@ -1356,7 +1356,7 @@ config MICROCODE_LATE_FORCE_MINREV
          revision check fails.
 
          This minimal revision check can also be controlled via the
-         "microcode.minrev" parameter on the kernel command line.
+         "microcode=force_minrev" parameter on the kernel command line.
 
          If unsure say Y.
 

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index b92e09a..7d59063 100644 (file)
--- 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);
 
 /*
  * Synchronization.
@@ -126,13 +125,32 @@ 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, sizeof(cmd_buf)) > 0) {
+               while ((s = strsep(&p, ","))) {
+                       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;