linux-kernel - [PATCH AUTOSEL 6.12 068/486] x86/microcode: Update the Intel processor flag scan check

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Message-Id: <20250505223922.2682012-68-sashal@kernel.org>
Date: Mon,  5 May 2025 18:32:24 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Sohil Mehta <sohil.mehta@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Sasha Levin <sashal@...nel.org>,
	x86@...nel.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de
Subject: [PATCH AUTOSEL 6.12 068/486] x86/microcode: Update the Intel processor flag scan check

From: Sohil Mehta <sohil.mehta@...el.com>

[ Upstream commit 7e6b0a2e4152f4046af95eeb46f8b4f9b2a7398d ]

The Family model check to read the processor flag MSR is misleading and
potentially incorrect. It doesn't consider Family while comparing the
model number. The original check did have a Family number but it got
lost/moved during refactoring.

intel_collect_cpu_info() is called through multiple paths such as early
initialization, CPU hotplug as well as IFS image load. Some of these
flows would be error prone due to the ambiguous check.

Correct the processor flag scan check to use a Family number and update
it to a VFM based one to make it more readable.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Link: https://lore.kernel.org/r/20250219184133.816753-4-sohil.mehta@intel.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/include/asm/intel-family.h   | 1 +
 arch/x86/kernel/cpu/microcode/intel.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/intel-family.h b/arch/x86/include/asm/intel-family.h
index 62d8b9448dc5c..c6198fbcc1d77 100644
--- a/arch/x86/include/asm/intel-family.h
+++ b/arch/x86/include/asm/intel-family.h
@@ -46,6 +46,7 @@
 #define INTEL_ANY			IFM(X86_FAMILY_ANY, X86_MODEL_ANY)
 
 #define INTEL_PENTIUM_PRO		IFM(6, 0x01)
+#define INTEL_PENTIUM_III_DESCHUTES	IFM(6, 0x05)
 
 #define INTEL_CORE_YONAH		IFM(6, 0x0E)
 
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 815fa67356a2d..cf635414ca6ab 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -74,7 +74,7 @@ void intel_collect_cpu_info(struct cpu_signature *sig)
 	sig->pf = 0;
 	sig->rev = intel_get_microcode_revision();
 
-	if (x86_model(sig->sig) >= 5 || x86_family(sig->sig) > 6) {
+	if (IFM(x86_family(sig->sig), x86_model(sig->sig)) >= INTEL_PENTIUM_III_DESCHUTES) {
 		unsigned int val[2];
 
 		/* get processor flags from MSR 0x17 */
-- 
2.39.5