Microcode updates can usually jump revisions. However, there is an erratum on Granite Rapids systems. If they "jump over" revision 0x1000405, they result in #MC. Avoid it. Signed-off-by: Chang S. Bae Reviewed-by: Dave Hansen Cc: --- V2 -> V3: * Shorten the changelog and rename the function (Boris) * Reduce the code comment (Dave) * Allow 0x1000405 loading. Thanks to Andrew, this fix got attention. * Collect Dave review tag. Thanks, Dave! Note: * GNR98 currently describes loading 0x1000405 itself is unsafe, but it will be updated to say okay with that. I will watch out the GNR98 changes. * Jumping from < 0x1000380 to 0x1000405 was identified as an issue, but 0x1000380 is the first revision as GNR products. So loading 0x1000405 in production systems should be okay. --- arch/x86/kernel/cpu/microcode/intel.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 1142183c950c..30a22388d4b1 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -309,6 +309,26 @@ static void save_microcode_patch(struct microcode_intel *patch) pr_err("Unable to allocate microcode memory size: %u\n", size); } +static bool revision_is_safe(struct cpu_signature *sig, u32 rev) +{ + u32 vfm = IFM(x86_family(sig->sig), x86_model(sig->sig)); + + /* + * Erratum GNR98 can cause #MC's if "jumping over" revision 0x1000405. + * Avoid the jumps. + */ + if (vfm == INTEL_GRANITERAPIDS_X && + x86_stepping(sig->sig) == 1 && + sig->pf & 0x95 && + sig->rev < 0x1000405 && + rev > 0x1000405) { + pr_err_once("Erratum GNR98: skipping revision 0x%x.\n", rev); + return false; + } + + return true; +} + /* Scan blob for microcode matching the boot CPUs family, model, stepping */ static __init struct microcode_intel *scan_microcode(void *data, size_t size, struct ucode_cpu_info *uci, @@ -330,6 +350,9 @@ static __init struct microcode_intel *scan_microcode(void *data, size_t size, if (!intel_find_matching_signature(data, &uci->cpu_sig)) continue; + if (!revision_is_safe(&uci->cpu_sig, mc_header->rev)) + continue; + /* * For saving the early microcode, find the matching revision which * was loaded on the BSP. @@ -878,6 +901,9 @@ static enum ucode_state parse_microcode_blobs(int cpu, struct iov_iter *iter) if (!intel_find_matching_signature(mc, &uci->cpu_sig)) continue; + if (!revision_is_safe(&uci->cpu_sig, mc_header.rev)) + continue; + is_safe = ucode_validate_minrev(&mc_header); if (force_minrev && !is_safe) continue; -- 2.53.0