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x86/microcode/intel: Reject problematic loading on Granite Rapids systems

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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 <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260916225939.1144524-1-chang.seok.bae@intel.com
This commit is contained in:
Chang S. Bae 2026-09-16 22:59:39 +00:00 committed by Borislav Petkov (AMD)
parent 27600805e6
commit e7d3e2f46d
1 changed files with 26 additions and 0 deletions
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26
arch/x86/kernel/cpu/microcode/intel.c
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@ -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;