Messages in this thread Patch in this message |  | | From | Andi Kleen <> | Subject | [PATCH 2/2] x86, microcode: Add option to allow downgrading of microcode | Date | Thu, 12 Dec 2013 15:57:48 -0800 |
| |
From: Andi Kleen <ak@linux.intel.com>
For testing purposes it can be useful to downgrade microcode. Normally the driver only allows upgrading.
Add a module_param (default off) that allows downgrading.
Note the module_param can currently not be set for early ucode update, only for late.
Signed-off-by: Andi Kleen <ak@linux.intel.com> --- arch/x86/kernel/microcode_intel_lib.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/microcode_intel_lib.c b/arch/x86/kernel/microcode_intel_lib.c index ce69320..18d5325 100644 --- a/arch/x86/kernel/microcode_intel_lib.c +++ b/arch/x86/kernel/microcode_intel_lib.c @@ -26,11 +26,16 @@ #include <linux/uaccess.h> #include <linux/kernel.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <asm/microcode_intel.h> #include <asm/processor.h> #include <asm/msr.h> +static bool allow_downgrade; +module_param(allow_downgrade, bool, 0644); +MODULE_PARM_DESC(allow_downgrade, "Allow downgrading microcode"); + static inline int update_match_cpu(unsigned int csig, unsigned int cpf, unsigned int sig, unsigned int pf) @@ -41,6 +46,8 @@ update_match_cpu(unsigned int csig, unsigned int cpf, int update_match_revision(struct microcode_header_intel *mc_header, int rev) { + if (allow_downgrade) + return 1; return (mc_header->rev <= rev) ? 0 : 1; } -- 1.8.3.1
|  |