tools/x86/kcpuid: Dump the CPUID function in detailed view

Sometimes it is useful to know which CPUID leaf contains the fields so
add it to -d output so that it looks like this:

  CPUID_0x8000001e_ECX[0x0]:
           extended_apic_id       : 0x8           - Extended APIC ID
           core_id                : 0x4           - Identifies the logical core ID
           threads_per_core       : 0x1           - The number of threads per core is threads_per_core + 1
           node_id                : 0x0           - Node ID
           nodes_per_processor    : 0x0           - Nodes per processor { 0: 1 node, else reserved }

  CPUID_0x8000001f_ECX[0x0]:
           sme                 -  Secure Memory Encryption

...
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Reviewed-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20230206141832.4162264-4-terry.bowman@amd.com

tools/arch/x86/kcpuid/kcpuid.c

@@ -33,7 +33,7 @@ struct reg_desc {
 	struct bits_desc descs[32];
 };
 
-enum {
+enum cpuid_reg {
 	R_EAX = 0,
 	R_EBX,
 	R_ECX,
@@ -41,6 +41,10 @@ enum {
 	NR_REGS
 };
 
+static const char * const reg_names[] = {
+	"EAX", "EBX", "ECX", "EDX",
+};
+
 struct subleaf {
 	u32 index;
 	u32 sub;
@@ -428,12 +432,18 @@ static void parse_text(void)
 
 
 /* Decode every eax/ebx/ecx/edx */
-static void decode_bits(u32 value, struct reg_desc *rdesc)
+static void decode_bits(u32 value, struct reg_desc *rdesc, enum cpuid_reg reg)
 {
 	struct bits_desc *bdesc;
 	int start, end, i;
 	u32 mask;
 
+	if (!rdesc->nr) {
+		if (show_details)
+			printf("\t %s: 0x%08x\n", reg_names[reg], value);
+		return;
+	}
+
 	for (i = 0; i < rdesc->nr; i++) {
 		bdesc = &rdesc->descs[i];
 
@@ -468,13 +478,21 @@ static void show_leaf(struct subleaf *leaf)
 	if (!leaf)
 		return;
 
-	if (show_raw)
+	if (show_raw) {
 		leaf_print_raw(leaf);
+	} else {
+		if (show_details)
+			printf("CPUID_0x%x_ECX[0x%x]:\n",
+				leaf->index, leaf->sub);
+	}
+
+	decode_bits(leaf->eax, &leaf->info[R_EAX], R_EAX);
+	decode_bits(leaf->ebx, &leaf->info[R_EBX], R_EBX);
+	decode_bits(leaf->ecx, &leaf->info[R_ECX], R_ECX);
+	decode_bits(leaf->edx, &leaf->info[R_EDX], R_EDX);
 
-	decode_bits(leaf->eax, &leaf->info[R_EAX]);
-	decode_bits(leaf->ebx, &leaf->info[R_EBX]);
-	decode_bits(leaf->ecx, &leaf->info[R_ECX]);
-	decode_bits(leaf->edx, &leaf->info[R_EDX]);
+	if (!show_raw && show_details)
+		printf("\n");
 }
 
 static void show_func(struct cpuid_func *func)