We don't refuse to load the affected microcodes; just refuse to use SPEC_CTRL if they're detected.
AMD has a feature bit for "PRED_CMD only", which Intel didn't do. When disabling SPEC_CTRL we can actually turn on that AMD bit to allow IBPB to still be used. We handle the other AMD bits here too, because hypervisors *may* have been exposing those bits even on Intel chips, for fine-grained control of what's available. Signed-off-by: David Woodhouse <[email protected]> --- arch/x86/kernel/cpu/intel.c | 76 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index b720dac..f5c7f61 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -102,6 +102,64 @@ static void probe_xeon_phi_r3mwait(struct cpuinfo_x86 *c) ELF_HWCAP2 |= HWCAP2_RING3MWAIT; } +/* + * Early microcode releases for the Spectre v2 mitigation were broken. + * Information taken from; + * • https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/microcode-update-guidance.pdf + * • https://kb.vmware.com/s/article/52345 + * • Microcode revisions observed in the wild + * • releasenote from 20180108 microcode release + */ +struct sku_microcode { + u8 model; + u8 stepping; + u32 microcode; +}; +static const struct sku_microcode spectre_bad_microcodes[] = { + { INTEL_FAM6_KABYLAKE_DESKTOP, 0x0B, 0x80 }, + /* Corrected typo in Intel doc */ + { INTEL_FAM6_KABYLAKE_DESKTOP, 0x0A, 0x80 }, + { INTEL_FAM6_KABYLAKE_MOBILE, 0x0A, 0x80 }, + { INTEL_FAM6_KABYLAKE_MOBILE, 0x09, 0x80 }, + { INTEL_FAM6_KABYLAKE_DESKTOP, 0x09, 0x80 }, + { INTEL_FAM6_SKYLAKE_X, 0x04, 0x0200003C }, + { INTEL_FAM6_SKYLAKE_MOBILE, 0x03, 0x000000C2 }, + { INTEL_FAM6_SKYLAKE_DESKTOP, 0x03, 0x000000C2 }, + { INTEL_FAM6_BROADWELL_CORE, 0x04, 0x28 }, + { INTEL_FAM6_BROADWELL_GT3E, 0x01, 0x0000001B }, + { INTEL_FAM6_HASWELL_ULT, 0x01, 0x21 }, + { INTEL_FAM6_HASWELL_GT3E, 0x01, 0x18 }, + { INTEL_FAM6_HASWELL_CORE, 0x03, 0x23 }, + { INTEL_FAM6_IVYBRIDGE_X, 0x04, 0x42a }, + { INTEL_FAM6_HASWELL_X, 0x02, 0x3b }, + { INTEL_FAM6_HASWELL_X, 0x04, 0x10 }, + { INTEL_FAM6_HASWELL_CORE, 0x03, 0x23 }, + { INTEL_FAM6_BROADWELL_XEON_D, 0x02, 0x14 }, + { INTEL_FAM6_BROADWELL_XEON_D, 0x03, 0x7000011 }, + { INTEL_FAM6_BROADWELL_GT3E, 0x01, 0x0000001B }, + { INTEL_FAM6_BROADWELL_X, 0x01, 0x0b000025 }, + /* Dropped repeat of KBL Desktop 906E9, 0x80 */ + { INTEL_FAM6_SKYLAKE_X, 0x03, 0x0100013e }, + /* Dropped repeat of SKX 50654, 0x200003c */ + /* Updated in the 20180108 release; blacklist until we know otherwise */ + { INTEL_FAM6_ATOM_GEMINI_LAKE, 0x01, 0x22 }, + /* Observed in the wild */ + { INTEL_FAM6_SANDYBRIDGE_X, 0x06, 0x61b }, + { INTEL_FAM6_SANDYBRIDGE_X, 0x07, 0x712 }, +}; + +static bool bad_spectre_microcode(struct cpuinfo_x86 *c) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) { + if (c->x86_model == spectre_bad_microcodes[i].model && + c->x86_mask == spectre_bad_microcodes[i].stepping) + return (c->microcode <= spectre_bad_microcodes[i].microcode); + } + return false; +} + static void early_init_intel(struct cpuinfo_x86 *c) { u64 misc_enable; @@ -122,6 +180,24 @@ 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(); + if ((cpu_has(c, X86_FEATURE_SPEC_CTRL) || + cpu_has(c, X86_FEATURE_STIBP) || + cpu_has(c, X86_FEATURE_AMD_SPEC_CTRL) || + cpu_has(c, X86_FEATURE_AMD_STIBP)) && bad_spectre_microcode(c)) { + pr_warn("Intel Spectre v2 broken microcode detected; disabling SPEC_CTRL\n"); + /* + * Intel's X86_FEATURE_SPEC_CTRL says both MSRs are available. + * We can't leave that set, but we can turn on the AMD bit + * which advertises PRED_CMD alone. IBPB is believed to be OK. + */ + if (cpu_has(c, X86_FEATURE_SPEC_CTRL)) + set_cpu_cap(c, X86_FEATURE_AMD_PRED_CMD); + clear_cpu_cap(c, X86_FEATURE_SPEC_CTRL); + clear_cpu_cap(c, X86_FEATURE_STIBP); + clear_cpu_cap(c, X86_FEATURE_AMD_SPEC_CTRL); + clear_cpu_cap(c, X86_FEATURE_AMD_STIBP); + } + /* * Atom erratum AAE44/AAF40/AAG38/AAH41: * -- 2.7.4
