From c84ba4cdf4c65eef0f94661ab4cf3895594546a1 Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Wed, 20 Aug 2025 11:58:57 +0200 Subject: [PATCH] x86/microcode/AMD: Handle the case of no BIOS microcode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit fcf8239ad6a5de54fa7ce18e464c6b5951b982cb upstream. Machines can be shipped without any microcode in the BIOS. Which means, the microcode patch revision is 0. Handle that gracefully. Fixes: 94838d230a6c ("x86/microcode/AMD: Use the family,model,stepping encoded in the patch ID") Reported-by: Vítek Vávra Signed-off-by: Borislav Petkov (AMD) Cc: Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/microcode/amd.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index 7444fe0e3d08..2cb30d9c5b4a 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -161,8 +161,28 @@ static int cmp_id(const void *key, const void *elem) return 1; } +static u32 cpuid_to_ucode_rev(unsigned int val) +{ + union zen_patch_rev p = {}; + union cpuid_1_eax c; + + c.full = val; + + p.stepping = c.stepping; + p.model = c.model; + p.ext_model = c.ext_model; + p.ext_fam = c.ext_fam; + + return p.ucode_rev; +} + static bool need_sha_check(u32 cur_rev) { + if (!cur_rev) { + cur_rev = cpuid_to_ucode_rev(bsp_cpuid_1_eax); + pr_info_once("No current revision, generating the lowest one: 0x%x\n", cur_rev); + } + switch (cur_rev >> 8) { case 0x80012: return cur_rev <= 0x800126f; break; case 0x80082: return cur_rev <= 0x800820f; break; @@ -744,8 +764,6 @@ static struct ucode_patch *cache_find_patch(struct ucode_cpu_info *uci, u16 equi n.equiv_cpu = equiv_cpu; n.patch_id = uci->cpu_sig.rev; - WARN_ON_ONCE(!n.patch_id); - list_for_each_entry(p, µcode_cache, plist) if (patch_cpus_equivalent(p, &n, false)) return p;