When microcode is loaded later after system boot, new microcode could enumerate new features. It might not be possible to use these new features unless they are loaded during early boot via initrd or from the BIOS in some cases.
This patch attempts to simply check if there are any differences in feature set and warns user to use early microcode load before using the new features. Suggested-by: Andi Kleen <[email protected]> Signed-off-by: Ashok Raj <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Tony Luck <[email protected]> Cc: Tim Chen <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Borislav Petkov <[email protected]> --- arch/x86/kernel/cpu/microcode/intel.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index f7c55b0..0e07035 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -39,6 +39,7 @@ #include <asm/tlbflush.h> #include <asm/setup.h> #include <asm/msr.h> +#include "../kernel/cpu/cpu.h" /* get_cpu_cap() */ static const char ucode_path[] = "kernel/x86/microcode/GenuineIntel.bin"; @@ -776,7 +777,7 @@ static int apply_microcode_intel(int cpu) { struct microcode_intel *mc; struct ucode_cpu_info *uci; - struct cpuinfo_x86 *c; + struct cpuinfo_x86 *c, new_cpuinfo; static int prev_rev; u32 rev; @@ -804,17 +805,23 @@ static int apply_microcode_intel(int cpu) return -1; } + c = &cpu_data(cpu); if (rev != prev_rev) { pr_info("updated to revision 0x%x, date = %04x-%02x-%02x\n", rev, mc->hdr.date & 0xffff, mc->hdr.date >> 24, (mc->hdr.date >> 16) & 0xff); + memset(&new_cpuinfo, 0, sizeof (struct cpuinfo_x86)); + get_cpu_cap(&new_cpuinfo); + if (memcmp(&c->x86_capability, &new_cpuinfo.x86_capability, + sizeof(new_cpuinfo.x86_capability))) { + pr_warn_once("New features found in loaded microcode, but will be ignored\n"); + pr_warn_once("Please consider either early loading through initrd/built-in or a potential BIOS update.\n"); + } prev_rev = rev; } - c = &cpu_data(cpu); - uci->cpu_sig.rev = rev; c->microcode = rev; -- 2.7.4
