x86/cacheinfo: Use enums for cache descriptor types

The leaf 0x2 one-byte cache descriptor types:

	CACHE_L1_INST
	CACHE_L1_DATA
	CACHE_L2
	CACHE_L3

are just discriminators to be used within the cache_table[] mapping.
Their specific values are irrelevant.

Use enums for such types.

Make the enum packed and static assert that its values remain within a
single byte so that the cache_table[] array size do not go out of hand.

Use a __CHECKER__ guard for the static_assert(sizeof(enum) == 1) line as
sparse ignores the __packed annotation on enums.

This is similar to:

  fe3944fb245a ("fs: Move enum rw_hint into a new header file")

for the core SCSI code.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/Z9rsTirs9lLfEPD9@lx-t490
Link: https://lore.kernel.org/r/20250324133324.23458-19-darwi@linutronix.de

2 files changed, 17 insertions, 7 deletions

diff --git a/arch/x86/include/asm/cpuid/types.h b/arch/x86/include/asm/cpuid/types.h
index 753f6c4514f4..39c3c79c081b 100644
--- a/arch/x86/include/asm/cpuid/types.h
+++ b/arch/x86/include/asm/cpuid/types.h
@@ -2,6 +2,7 @@
 #ifndef _ASM_X86_CPUID_TYPES_H
 #define _ASM_X86_CPUID_TYPES_H
 
+#include <linux/build_bug.h>
 #include <linux/types.h>
 
 /*
@@ -45,4 +46,18 @@ union leaf_0x2_regs {
 	u8			desc[16];
 };
 
+/*
+ * Leaf 0x2 1-byte descriptors' cache types
+ * To be used for their mappings at cache_table[]
+ */
+enum _cache_table_type {
+	CACHE_L1_INST,
+	CACHE_L1_DATA,
+	CACHE_L2,
+	CACHE_L3,
+} __packed;
+#ifndef __CHECKER__
+static_assert(sizeof(enum _cache_table_type) == 1);
+#endif
+
 #endif /* _ASM_X86_CPUID_TYPES_H */
diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 626f55f960dc..09c5aa9af973 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -23,11 +23,6 @@
 
 #include "cpu.h"
 
-#define CACHE_L1_INST	1
-#define CACHE_L1_DATA	2
-#define CACHE_L2	3
-#define CACHE_L3	4
-
 /* Shared last level cache maps */
 DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
 
@@ -41,7 +36,7 @@ unsigned int memory_caching_control __ro_after_init;
 
 struct _cache_table {
 	u8 descriptor;
-	char cache_type;
+	enum _cache_table_type type;
 	short size;
 };
 
@@ -520,7 +515,7 @@ void init_intel_cacheinfo(struct cpuinfo_x86 *c)
 			if (!entry)
 				continue;
 
-			switch (entry->cache_type) {
+			switch (entry->type) {
 			case CACHE_L1_INST:	l1i += entry->size; break;
 			case CACHE_L1_DATA:	l1d += entry->size; break;
 			case CACHE_L2:		l2  += entry->size; break;