x86/selftests: Skip the tests if prerequisites aren't fulfilled

commit 99c8431 upstream.

Skip instead of failing when prerequisite conditions aren't fulfilled,
such as invalid xstate values etc.

Make the tests show as 'SKIP' when run:

  make -C tools/testing/selftests/ TARGETS=x86 run_tests

  ...
  # timeout set to 45
  # selftests: x86: amx_64
  # # xstate cpuid: invalid tile data size/offset: 0/0
  ok 42 selftests: x86: amx_64 # SKIP
  # timeout set to 45
  # selftests: x86: lam_64
  # # Unsupported LAM feature!
  ok 43 selftests: x86: lam_64 # SKIP
  ...

In the AMX test, Move away from check_cpuid_xsave() and start using
arch_prctl() to find out if AMX support is present or not. In the
kernels where AMX isn't present, arch_prctl() returns -EINVAL, hence it is
backward compatible.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20240327111720.3509180-1-usama.anjum@collabora.com
[ Zelin Deng: ANBZ: #8853 ]
Link: https://gitee.com/anolis/cloud-kernel/pulls/3125
Signed-off-by: Zelin Deng <zelin.deng@linux.alibaba.com>
[ WangYuli: Edit commit msg. ]
[ Backport from v6.9 ]
Signed-off-by: WangYuli <wangyuli@uniontech.com>

Author: Muhammad Usama Anjum

tools/testing/selftests/x86/amx.c

@@ -103,21 +103,6 @@ static void clearhandler(int sig)
 
 #define CPUID_LEAF1_ECX_XSAVE_MASK	(1 << 26)
 #define CPUID_LEAF1_ECX_OSXSAVE_MASK	(1 << 27)
-static inline void check_cpuid_xsave(void)
-{
-	uint32_t eax, ebx, ecx, edx;
-
-	/*
-	 * CPUID.1:ECX.XSAVE[bit 26] enumerates general
-	 * support for the XSAVE feature set, including
-	 * XGETBV.
-	 */
-	__cpuid_count(1, 0, eax, ebx, ecx, edx);
-	if (!(ecx & CPUID_LEAF1_ECX_XSAVE_MASK))
-		fatal_error("cpuid: no CPU xsave support");
-	if (!(ecx & CPUID_LEAF1_ECX_OSXSAVE_MASK))
-		fatal_error("cpuid: no OS xsave support");
-}
 
 static uint32_t xbuf_size;
 
@@ -350,6 +335,7 @@ enum expected_result { FAIL_EXPECTED, SUCCESS_EXPECTED };
 
 /* arch_prctl() and sigaltstack() test */
 
+#define ARCH_GET_XCOMP_SUPP	0x1021
 #define ARCH_GET_XCOMP_PERM	0x1022
 #define ARCH_REQ_XCOMP_PERM	0x1023
 
@@ -928,8 +914,15 @@ static void test_ptrace(void)
 
 int main(void)
 {
-	/* Check hardware availability at first */
-	check_cpuid_xsave();
+	unsigned long features;
+	long rc;
+
+	rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_SUPP, &features);
+	if (rc || (features & XFEATURE_MASK_XTILE) != XFEATURE_MASK_XTILE) {
+		ksft_print_msg("no AMX support\n");
+		return KSFT_SKIP;
+	}
+
 	check_cpuid_xtiledata();
 
 	init_stashed_xsave();

tools/testing/selftests/x86/lam.c

@@ -1183,7 +1183,7 @@ int main(int argc, char **argv)
 
 	if (!cpu_has_lam()) {
 		ksft_print_msg("Unsupported LAM feature!\n");
-		return -1;
+		return KSFT_SKIP;
 	}
 
 	while ((c = getopt(argc, argv, "ht:")) != -1) {