From e7d3e2f46dd5a69046e6d95a0f189155a5516b93 Mon Sep 17 00:00:00 2001 From: "Chang S. Bae" Date: Wed, 16 Sep 2026 22:59:39 +0000 Subject: [PATCH] x86/microcode/intel: Reject problematic loading on Granite Rapids systems Microcode updates can usually jump revisions. However, there is an erratum on Granite Rapids systems. If they "jump over" revision 0x1000405, they result in an #MC. Avoid it. Signed-off-by: Chang S. Bae Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260916225939.1144524-1-chang.seok.bae@intel.com --- 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..9f09d388ed20 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 #MCs 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;