selftests/x86/xstate: Enumerate and name xstate components

After moving essential helpers from amx.c, the code remains neutral
regarding which xstate components it handles. However, explicitly listing
known components helps users identify which features are ready for
testing.

Enumerate xstate components to facilitate identification. Extend struct
xstate_info to include a name field, providing a human-readable
identifier.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250226010731.2456-4-chang.seok.bae@intel.com

tools/testing/selftests/x86/amx.c

@@ -29,8 +29,6 @@
 /* err() exits and will not return */
 #define fatal_error(msg, ...)	err(1, "[FAIL]\t" msg, ##__VA_ARGS__)
 
-#define XFEATURE_XTILECFG	17
-#define XFEATURE_XTILEDATA	18
 #define XFEATURE_MASK_XTILECFG	(1 << XFEATURE_XTILECFG)
 #define XFEATURE_MASK_XTILEDATA	(1 << XFEATURE_XTILEDATA)
 #define XFEATURE_MASK_XTILE	(XFEATURE_MASK_XTILECFG | XFEATURE_MASK_XTILEDATA)

tools/testing/selftests/x86/xstate.h

@@ -9,6 +9,59 @@
 #define XSAVE_HDR_OFFSET	512
 #define XSAVE_HDR_SIZE		64
 
+/*
+ * List of XSAVE features Linux knows about. Copied from
+ * arch/x86/include/asm/fpu/types.h
+ */
+enum xfeature {
+	XFEATURE_FP,
+	XFEATURE_SSE,
+	XFEATURE_YMM,
+	XFEATURE_BNDREGS,
+	XFEATURE_BNDCSR,
+	XFEATURE_OPMASK,
+	XFEATURE_ZMM_Hi256,
+	XFEATURE_Hi16_ZMM,
+	XFEATURE_PT_UNIMPLEMENTED_SO_FAR,
+	XFEATURE_PKRU,
+	XFEATURE_PASID,
+	XFEATURE_CET_USER,
+	XFEATURE_CET_KERNEL_UNUSED,
+	XFEATURE_RSRVD_COMP_13,
+	XFEATURE_RSRVD_COMP_14,
+	XFEATURE_LBR,
+	XFEATURE_RSRVD_COMP_16,
+	XFEATURE_XTILECFG,
+	XFEATURE_XTILEDATA,
+
+	XFEATURE_MAX,
+};
+
+/* Copied from arch/x86/kernel/fpu/xstate.c */
+static const char *xfeature_names[] =
+{
+	"x87 floating point registers",
+	"SSE registers",
+	"AVX registers",
+	"MPX bounds registers",
+	"MPX CSR",
+	"AVX-512 opmask",
+	"AVX-512 Hi256",
+	"AVX-512 ZMM_Hi256",
+	"Processor Trace (unused)",
+	"Protection Keys User registers",
+	"PASID state",
+	"Control-flow User registers",
+	"Control-flow Kernel registers (unused)",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"AMX Tile config",
+	"AMX Tile data",
+	"unknown xstate feature",
+};
+
 struct xsave_buffer {
 	union {
 		struct {
@@ -58,6 +111,7 @@ static inline uint32_t get_xbuf_size(void)
 }
 
 struct xstate_info {
+	const char *name;
 	uint32_t num;
 	uint32_t mask;
 	uint32_t xbuf_offset;
@@ -69,6 +123,12 @@ static inline struct xstate_info get_xstate_info(uint32_t xfeature_num)
 	struct xstate_info xstate = { };
 	uint32_t eax, ebx, ecx, edx;
 
+	if (xfeature_num >= XFEATURE_MAX) {
+		ksft_print_msg("unknown state\n");
+		return xstate;
+	}
+
+	xstate.name = xfeature_names[xfeature_num];
 	xstate.num  = xfeature_num;
 	xstate.mask = 1 << xfeature_num;