Skip to contentSkip to conversation

x86/microcode/AMD: Move the no-revision fixup to get_patch_level()

PATCH New Borislav Petkov 2 participants 2 messages May 30 – Jun 3

Subsystems (2)
x86 x86 microcode update support
lore
Share & tools
lore

Borislav Petkov

author
#0 lore raw

PATCH 1/1 x86/microcode/AMD: Move the no-revision fixup to get_patch_level()

From: "Borislav Petkov (AMD)" <[email protected]>

On machines which don't have microcode applied yet, the revision is 0. However, this doesn't work with the Zen family/model/stepping patch arithmetic. So move the fixup to the patch level getter function and this way make sure the patch level is always proper and thus the arithmetic always works.

Signed-off-by Borislav Petkov (AMD) <[email protected]>
---
 arch/x86/kernel/cpu/microcode/amd.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)
arch/x86/kernel/cpu/microcode/amd.c +4 -5
index e533881284a1..f03890eec333 100644
@@ -233,11 +233,6 @@ static bool need_sha_check(u32 cur_rev)
 {
 	u32 cutoff;
 
-	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);
-	}
-
 	cutoff = get_cutoff_revision(cur_rev);
 	if (cutoff)
 		return cur_rev <= cutoff;

@@ -338,6 +333,10 @@ static u32 get_patch_level(void)
 	}
 
 	native_rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
+	if (!rev) {
+		rev = cpuid_to_ucode_rev(bsp_cpuid_1_eax);
+		pr_info_once("No current revision, generating the lowest one: 0x%x\n", rev);
+	}
 
 	return rev;
 }
Signature · 1 line
2.53.0
maintainer
#1 lore raw

PATCH 1/1 x86/microcode/AMD: Move the no-revision fixup to get_patch_level()

Quoted 8 lines · Borislav Petkov

From: "Borislav Petkov (AMD)" <[email protected]>

On machines which don't have microcode applied yet, the revision is 0. However, this doesn't work with the Zen family/model/stepping patch arithmetic. So move the fixup to the patch level getter function and this way make sure the patch level is always proper and thus the arithmetic always works.

Quoted 4 lines
Signed-off-by Borislav Petkov (AMD) <[email protected]>
---
 arch/x86/kernel/cpu/microcode/amd.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

AI review caught something, here's v2:

---
From: "Borislav Petkov (AMD)" <[email protected]>
Date: Fri, 29 May 2026 17:27:24 -0700
Subject: [PATCH -v2] x86/microcode/AMD: Move the no-revision fixup to get_patch_level()

On machines which don't have microcode applied yet, the revision is 0. However, this doesn't work with the Zen family/model/stepping patch arithmetic. So move the fixup to the patch level getter function and this way make sure the patch level is always proper and thus the arithmetic always works.

And now that it can be called on any family, make this Zen-only.

Assisted-by claude/claude-opus-4-6
Signed-off-by Borislav Petkov (AMD) <[email protected]>
---
 arch/x86/kernel/cpu/microcode/amd.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
arch/x86/kernel/cpu/microcode/amd.c +7 -5
index e533881284a1..b90af74b8be9 100644
@@ -233,11 +233,6 @@ static bool need_sha_check(u32 cur_rev)
 {
 	u32 cutoff;
 
-	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);
-	}
-
 	cutoff = get_cutoff_revision(cur_rev);
 	if (cutoff)
 		return cur_rev <= cutoff;

@@ -338,6 +333,13 @@ static u32 get_patch_level(void)
 	}
 
 	native_rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
+	if (!rev) {
+		if (x86_family(bsp_cpuid_1_eax) < 0x17)
+			return rev;
+
+		rev = cpuid_to_ucode_rev(bsp_cpuid_1_eax);
+		pr_info_once("No current revision, generating the lowest one: 0x%x\n", rev);
+	}
 
 	return rev;
 }
Signature · 7 lines
2.53.0

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette