From: Dave Hansen Date: Wed, 4 Mar 2026 18:10:20 +0000 (-0800) Subject: x86/cpu: Add platform ID to CPU info structure X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d8630b67ca1edeea728dbb309b09d239e9db6bdf;p=thirdparty%2Fkernel%2Flinux.git x86/cpu: Add platform ID to CPU info structure The end goal here is to be able to do x86_match_cpu() and match on a specific platform ID. While it would be possible to stash this ID off somewhere or read it dynamically, that approaches would not be consistent with the other fields which can be matched. Read the platform ID and store it in cpuinfo_x86. There are lots of sites to set this new field. Place it near the place c->microcode is established since the platform ID is so closely intertwined with microcode updates. Note: This should not grow the size of 'struct cpuinfo_x86' in practice since the u8 fits next to another u8 in the structure. Signed-off-by: Dave Hansen Reviewed-by: Sohil Mehta Reviewed-by: Pawan Gupta Link: https://patch.msgid.link/20260304181020.8D518228@davehans-spike.ostc.intel.com --- diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h index 8b41f26f003b0..3c317d1557716 100644 --- a/arch/x86/include/asm/microcode.h +++ b/arch/x86/include/asm/microcode.h @@ -61,6 +61,8 @@ static inline int intel_microcode_get_datasize(struct microcode_header_intel *hd return hdr->datasize ? : DEFAULT_UCODE_DATASIZE; } +extern u32 intel_get_platform_id(void); + static inline u32 intel_get_microcode_revision(void) { u32 rev, dummy; diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index a24c7805acdb5..10b5355b323e2 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -140,6 +140,11 @@ struct cpuinfo_x86 { __u32 x86_vfm; }; __u8 x86_stepping; + union { + // MSR_IA32_PLATFORM_ID[52-50] + __u8 intel_platform_id; + __u8 amd_unused; + }; #ifdef CONFIG_X86_64 /* Number of 4K pages in DTLB/ITLB combined(in pages): */ int x86_tlbsize; diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 646ff33c4651d..f28c0efb7c8f1 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -205,6 +205,7 @@ static void early_init_intel(struct cpuinfo_x86 *c) if (c->x86 >= 6 && !cpu_has(c, X86_FEATURE_IA64)) c->microcode = intel_get_microcode_revision(); + c->intel_platform_id = intel_get_platform_id(); /* Now if any of them are set, check the blacklist and clear the lot */ if ((cpu_has(c, X86_FEATURE_SPEC_CTRL) || diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 83c6cd23d6483..37ac4afe09724 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -134,7 +134,7 @@ static u32 intel_cpuid_vfm(void) return IFM(fam, model); } -static u32 intel_get_platform_id(void) +u32 intel_get_platform_id(void) { unsigned int val[2];