From: Zhang Rui <rui.zhang@intel.com>
Date: Mon, 26 Jan 2026 00:27:01 +0000 (+0800)
Subject: tools/power/x86/intel-speed-select: Fix cpu extended family ID decoding
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=df4a83543117c7fc27077fd7f4ffe870556b257b;p=thirdparty%2Flinux.git

tools/power/x86/intel-speed-select: Fix cpu extended family ID decoding

When decode and use CPU extended family ID in intel-speed-select, there
are several potential issues,
1. Mask with 0x0f to get CPU extended family ID is bogus because
   CPU extended family ID takes 8 bits (bit 27:20).
2. Use CPU extended family ID fields without checking CPU family ID is
   risky. Because Intel SDM says, "The Extended Family ID needs to be
   examined only when the Family ID is 0FH."
3. Saving cpu family ID and cpu extended family ID separately doesn't
   align with Linux kernel. And it may bring extra complexity when
   making family specific changes in the future.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---

diff --git a/tools/power/x86/intel-speed-select/isst-config.c b/tools/power/x86/intel-speed-select/isst-config.c
index 652ef1f567ad..3f2573ecca76 100644
--- a/tools/power/x86/intel-speed-select/isst-config.c
+++ b/tools/power/x86/intel-speed-select/isst-config.c
@@ -26,7 +26,7 @@ static FILE *outf;
 
 static int cpu_model;
 static int cpu_stepping;
-static int extended_family;
+static int cpu_family;
 
 #define MAX_CPUS_IN_ONE_REQ 512
 static short max_target_cpus;
@@ -158,7 +158,7 @@ int is_icx_platform(void)
 
 static int is_dmr_plus_platform(void)
 {
-	if (extended_family == 0x04)
+	if (cpu_family == 19)
 		return 1;
 
 	return 0;
@@ -167,13 +167,14 @@ static int is_dmr_plus_platform(void)
 static int update_cpu_model(void)
 {
 	unsigned int ebx, ecx, edx;
-	unsigned int fms, family;
+	unsigned int fms;
 
 	__cpuid(1, fms, ebx, ecx, edx);
-	family = (fms >> 8) & 0xf;
-	extended_family = (fms >> 20) & 0x0f;
+	cpu_family = (fms >> 8) & 0xf;
+	if (cpu_family == 0xf)
+		cpu_family += (fms >> 20) & 0xff;
 	cpu_model = (fms >> 4) & 0xf;
-	if (family == 6 || family == 0xf)
+	if (cpu_family == 6 || cpu_family == 0xf)
 		cpu_model += ((fms >> 16) & 0xf) << 4;
 
 	cpu_stepping = fms & 0xf;