From: Andi Kleen ak@linux.intel.com
The Intel microcode revision space is unsigned. Inside Intel there are special microcode revisions that have the highest bit set, and they are considered to have a higher revision than any microcodes that don't have this bit set.
The function comparing the microcode revision in the Linux driver compares u32 with int, which ends up being signed extended to long on 64bit systems. This results in these highest bit set microcode revision not loading because their revision appears negative and smaller than the existing microcode.
Change the comparison to unsigned. With that the loading works as expected.
Cc: stable@vger.kernel.org # Any supported stable Signed-off-by: Andi Kleen ak@linux.intel.com -- v2: White space changes. v3: Be more verbose --- arch/x86/kernel/cpu/microcode/intel.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 16936a24795c..e54d402500d3 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -93,7 +93,8 @@ static int find_matching_signature(void *mc, unsigned int csig, int cpf) /* * Returns 1 if update has been found, 0 otherwise. */ -static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev) +static int has_newer_microcode(void *mc, unsigned int csig, int cpf, + unsigned new_rev) { struct microcode_header_intel *mc_hdr = mc;