From f3e2a51f568d9f33370f4e8bb05669a34223241a Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Mon, 9 Jan 2017 12:41:44 +0100 Subject: [PATCH] x86/microcode: Use native CPUID to tickle out microcode revision Intel supplies the microcode revision value in MSR 0x8b (IA32_BIOS_SIGN_ID) after CPUID(1) has been executed. Execute it each time before reading that MSR. It used to do sync_core() which did do CPUID but c198b121b1a1 ("x86/asm: Rewrite sync_core() to use IRET-to-self") changed the sync_core() implementation so we better make the microcode loading case explicit, as the SDM documents it. Reported-and-tested-by: Jun'ichi Nomura Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/20170109114147.5082-3-bp@alien8.de Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/intel.c | 2 +- arch/x86/kernel/cpu/microcode/intel.c | 26 +++----------------------- 2 files changed, 4 insertions(+), 24 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index fcd484d2bb03..2d49aa949fa1 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -83,7 +83,7 @@ static void early_init_intel(struct cpuinfo_x86 *c) wrmsr(MSR_IA32_UCODE_REV, 0, 0); /* Required by the SDM */ - sync_core(); + native_cpuid_eax(1); rdmsr(MSR_IA32_UCODE_REV, lower_word, c->microcode); } diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index b624b54912e1..f79249fab389 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -368,26 +368,6 @@ next: return patch; } -static void cpuid_1(void) -{ - /* - * According to the Intel SDM, Volume 3, 9.11.7: - * - * CPUID returns a value in a model specific register in - * addition to its usual register return values. The - * semantics of CPUID cause it to deposit an update ID value - * in the 64-bit model-specific register at address 08BH - * (IA32_BIOS_SIGN_ID). If no update is present in the - * processor, the value in the MSR remains unmodified. - * - * Use native_cpuid -- this code runs very early and we don't - * want to mess with paravirt. - */ - unsigned int eax = 1, ebx, ecx = 0, edx; - - native_cpuid(&eax, &ebx, &ecx, &edx); -} - static int collect_cpu_info_early(struct ucode_cpu_info *uci) { unsigned int val[2]; @@ -413,7 +393,7 @@ static int collect_cpu_info_early(struct ucode_cpu_info *uci) native_wrmsrl(MSR_IA32_UCODE_REV, 0); /* As documented in the SDM: Do a CPUID 1 here */ - cpuid_1(); + native_cpuid_eax(1); /* get the current revision from MSR 0x8B */ native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]); @@ -613,7 +593,7 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early) native_wrmsrl(MSR_IA32_UCODE_REV, 0); /* As documented in the SDM: Do a CPUID 1 here */ - cpuid_1(); + native_cpuid_eax(1); /* get the current revision from MSR 0x8B */ native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]); @@ -825,7 +805,7 @@ static int apply_microcode_intel(int cpu) wrmsrl(MSR_IA32_UCODE_REV, 0); /* As documented in the SDM: Do a CPUID 1 here */ - cpuid_1(); + native_cpuid_eax(1); /* get the current revision from MSR 0x8B */ rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]); -- 2.39.5