selftests/x86/xstate: Consolidate test invocations into a single entry

Currently, each of the three xstate tests runs as a separate invocation,
requiring the xstate number to be passed and state information to be
reconstructed repeatedly. This approach arose from their individual and
isolated development, but now it makes sense to unify them.

Introduce a wrapper function that first verifies feature availability
from the kernel and constructs the necessary state information once. The
wrapper then sequentially invokes all tests to ensure consistent
execution.

Update the AMX test to use this unified invocation.

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/20250226010731.2456-8-chang.seok.bae@intel.com

Author: ChangSeokBae

tools/testing/selftests/x86/amx.c

@@ -480,7 +480,6 @@ static void test_fork(void)
 
 int main(void)
 {
-	const unsigned int ctxtsw_num_threads = 5, ctxtsw_iterations = 10;
 	unsigned long features;
 	long rc;
 
@@ -506,11 +505,11 @@ int main(void)
 
 	test_fork();
 
-	test_context_switch(XFEATURE_XTILEDATA, ctxtsw_num_threads, ctxtsw_iterations);
-
-	test_ptrace(XFEATURE_XTILEDATA);
-
-	test_signal(XFEATURE_XTILEDATA);
+	/*
+	 * Perform generic xstate tests for context switching, ptrace,
+	 * and signal.
+	 */
+	test_xstate(XFEATURE_XTILEDATA);
 
 	clearhandler(SIGILL);
 	free_stashed_xsave();

tools/testing/selftests/x86/xstate.c

@@ -6,7 +6,9 @@
 #include <pthread.h>
 #include <stdbool.h>
 
+#include <asm/prctl.h>
 #include <sys/ptrace.h>
+#include <sys/syscall.h>
 #include <sys/uio.h>
 #include <sys/wait.h>
 
@@ -189,15 +191,13 @@ static void affinitize_cpu0(void)
 		ksft_exit_fail_msg("sched_setaffinity to CPU 0 failed\n");
 }
 
-void test_context_switch(uint32_t feature_num, uint32_t num_threads, uint32_t iterations)
+static void test_context_switch(uint32_t num_threads, uint32_t iterations)
 {
 	struct futex_info *finfo;
 
 	/* Affinitize to one CPU to force context switches */
 	affinitize_cpu0();
 
-	xstate = get_xstate_info(feature_num);
-
 	printf("[RUN]\t%s: check context switches, %d iterations, %d threads.\n",
 	       xstate.name, iterations, num_threads);
 
@@ -299,13 +299,11 @@ static void ptracer_inject_xstate(pid_t target)
 	free(xbuf2);
 }
 
-void test_ptrace(uint32_t feature_num)
+static void test_ptrace(void)
 {
 	pid_t child;
 	int status;
 
-	xstate = get_xstate_info(feature_num);
-
 	child = fork();
 	if (child < 0) {
 		ksft_exit_fail_msg("fork() failed\n");
@@ -392,17 +390,14 @@ static void validate_sigfpstate(int sig, siginfo_t *si, void *ctx_void)
 	copy_xstate(stashed_xbuf, xbuf);
 }
 
-void test_signal(uint32_t feature_num)
+static void test_signal(void)
 {
 	bool valid_xstate;
 
-	xstate = get_xstate_info(feature_num);
-
 	/*
 	 * The signal handler will access this to verify xstate context
 	 * preservation.
 	 */
-
 	stashed_xbuf = alloc_xbuf();
 	if (!stashed_xbuf)
 		ksft_exit_fail_msg("unable to allocate XSAVE buffer\n");
@@ -433,3 +428,26 @@ void test_signal(uint32_t feature_num)
 	clearhandler(SIGUSR1);
 	free(stashed_xbuf);
 }
+
+void test_xstate(uint32_t feature_num)
+{
+	const unsigned int ctxtsw_num_threads = 5, ctxtsw_iterations = 10;
+	unsigned long features;
+	long rc;
+
+	rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_SUPP, &features);
+	if (rc || !(features & (1 << feature_num))) {
+		ksft_print_msg("The kernel does not support feature number: %u\n", feature_num);
+		return;
+	}
+
+	xstate = get_xstate_info(feature_num);
+	if (!xstate.size || !xstate.xbuf_offset) {
+		ksft_exit_fail_msg("invalid state size/offset (%d/%d)\n",
+				   xstate.size, xstate.xbuf_offset);
+	}
+
+	test_context_switch(ctxtsw_num_threads, ctxtsw_iterations);
+	test_ptrace();
+	test_signal();
+}

tools/testing/selftests/x86/xstate.h

@@ -189,8 +189,7 @@ static inline void set_rand_data(struct xstate_info *xstate, struct xsave_buffer
 		*ptr = data;
 }
 
-void test_context_switch(uint32_t feature_num, uint32_t num_threads, uint32_t iterations);
-void test_ptrace(uint32_t feature_num);
-void test_signal(uint32_t feature_num);
+/* Testing kernel's context switching and ABI support for the xstate. */
+void test_xstate(uint32_t feature_num);
 
 #endif /* __SELFTESTS_X86_XSTATE_H */