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x86/microcode: Add microcode= cmdline parsing

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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
This commit is contained in:
Borislav Petkov (AMD) 2025-08-20 15:50:42 +02:00
parent 855042367e
commit 632ff61706
3 changed files with 30 additions and 8 deletions
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8
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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.

4
arch/x86/Kconfig
View File

@ -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.

26
arch/x86/kernel/cpu/microcode/core.c
View File

@ -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;