x86/microcode/AMD: Handle the case of no BIOS microcode

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 <vit.vavra.kh@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index 765b4646648f7b398a7ef52707c26681f66f10e5..910accfeb7856924934ab7e45173a65f9ea287c6 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -159,8 +159,28 @@ 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;
@@ -741,8 +761,6 @@ 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, &microcode_cache, plist)
                if (patch_cpus_equivalent(p, &n, false))
                        return p;