linux-kernel - [PATCH 2/2] selftests/x86/amx: Fix the test to avoid failure when AMX is unavailable

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Date:   Fri,  1 Apr 2022 15:10:14 -0700
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     linux-kselftest@...r.kernel.org, shuah@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     dave.hansen@...ux.intel.com, tglx@...utronix.de, bp@...e.de,
        chang.seok.bae@...el.com
Subject: [PATCH 2/2] selftests/x86/amx: Fix the test to avoid failure when AMX is unavailable

When a CPU does not have AMX, the test fails. But this is wrong as it
should be runnable regardless. Skip the test instead.

Reported-by: Thomas Gleixner <tglx@...utronix.de>
Fixes: 6a3e0651b4a ("selftests/x86/amx: Add test cases for AMX state management")
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 tools/testing/selftests/x86/amx.c | 42 +++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/x86/amx.c b/tools/testing/selftests/x86/amx.c
index 3615ef4a48bb..14abb6072a7d 100644
--- a/tools/testing/selftests/x86/amx.c
+++ b/tools/testing/selftests/x86/amx.c
@@ -106,6 +106,12 @@ static void clearhandler(int sig)
 
 #define CPUID_LEAF1_ECX_XSAVE_MASK	(1 << 26)
 #define CPUID_LEAF1_ECX_OSXSAVE_MASK	(1 << 27)
+
+static struct {
+	unsigned xsave:   1;
+	unsigned osxsave: 1;
+} cpuinfo;
+
 static inline void check_cpuid_xsave(void)
 {
 	uint32_t eax, ebx, ecx, edx;
@@ -118,10 +124,8 @@ static inline void check_cpuid_xsave(void)
 	eax = 1;
 	ecx = 0;
 	cpuid(&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");
+	cpuinfo.xsave = !!(ecx & CPUID_LEAF1_ECX_XSAVE_MASK);
+	cpuinfo.osxsave = !!(ecx & CPUID_LEAF1_ECX_OSXSAVE_MASK);
 }
 
 static uint32_t xbuf_size;
@@ -161,14 +165,31 @@ static void check_cpuid_xtiledata(void)
 	 * eax: XTILEDATA state component size
 	 * ebx: XTILEDATA state component offset in user buffer
 	 */
-	if (!eax || !ebx)
-		fatal_error("xstate cpuid: invalid tile data size/offset: %d/%d",
-				eax, ebx);
-
 	xtiledata.size	      = eax;
 	xtiledata.xbuf_offset = ebx;
 }
 
+static bool amx_available(void)
+{
+	check_cpuid_xsave();
+	if (!cpuinfo.xsave) {
+		printf("[SKIP]\tcpuid: no CPU xsave support\n");
+		return false;
+	} else if (!cpuinfo.osxsave) {
+		printf("[SKIP]\tcpuid: no OS xsave support\n");
+		return false;
+	}
+
+	check_cpuid_xtiledata();
+	if (!xtiledata.size || !xtiledata.xbuf_offset) {
+		printf("[SKIP]\txstate cpuid: no tile data (size/offset: %d/%d)\n",
+		       xtiledata.size, xtiledata.xbuf_offset);
+		return false;
+	}
+
+	return true;
+}
+
 /* The helpers for managing XSAVE buffer and tile states: */
 
 struct xsave_buffer *alloc_xbuf(void)
@@ -826,9 +847,8 @@ static void test_context_switch(void)
 
 int main(void)
 {
-	/* Check hardware availability at first */
-	check_cpuid_xsave();
-	check_cpuid_xtiledata();
+	if (!amx_available())
+		return 0;
 
 	init_stashed_xsave();
 	sethandler(SIGILL, handle_noperm, 0);
-- 
2.17.1