[PATCH v4 2/2] selftests/x86/amx: Update the ARCH_REQ_XCOMP_PERM test

[PATCH v4 2/2] selftests/x86/amx: Update the ARCH_REQ_XCOMP_PERM test

[Chang S. Bae]

Update the arch_prctl test to check the permission bitmap whether the
requested feature is added as expected or not.

Every non-dynamic feature that is enabled is permitted already for use.
TILECFG is not dynamic feature. Ensure the bit is always on from
ARCH_GET_XCOMP_PERM.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kselftest@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
---
 tools/testing/selftests/x86/amx.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/x86/amx.c b/tools/testing/selftests/x86/amx.c
index 3615ef4a48bb..e1e2c8f3356f 100644
--- a/tools/testing/selftests/x86/amx.c
+++ b/tools/testing/selftests/x86/amx.c
@@ -368,9 +368,16 @@ static void req_xtiledata_perm(void)
 
 static void validate_req_xcomp_perm(enum expected_result exp)
 {
-	unsigned long bitmask;
+	unsigned long bitmask, expected_bitmask;
 	long rc;
 
+	rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_PERM, &bitmask);
+	if (rc) {
+		fatal_error("prctl(ARCH_GET_XCOMP_PERM) error: %ld", rc);
+	} else if (!(bitmask & XFEATURE_MASK_XTILECFG)) {
+		fatal_error("ARCH_GET_XCOMP_PERM returns XFEATURE_XTILECFG off.");
+	}
+
 	rc = syscall(SYS_arch_prctl, ARCH_REQ_XCOMP_PERM, XFEATURE_XTILEDATA);
 	if (exp == FAIL_EXPECTED) {
 		if (rc) {
@@ -383,10 +390,15 @@ static void validate_req_xcomp_perm(enum expected_result exp)
 		fatal_error("ARCH_REQ_XCOMP_PERM saw unexpected failure.\n");
 	}
 
+	expected_bitmask = bitmask | XFEATURE_MASK_XTILEDATA;
+
 	rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_PERM, &bitmask);
 	if (rc) {
 		fatal_error("prctl(ARCH_GET_XCOMP_PERM) error: %ld", rc);
-	} else if (bitmask & XFEATURE_MASK_XTILE) {
+	} else if (bitmask != expected_bitmask) {
+		fatal_error("ARCH_REQ_XCOMP_PERM saw a wrong bitmask: %lx, expected: %lx.\n",
+			    bitmask, expected_bitmask);
+	} else {
 		printf("\tARCH_REQ_XCOMP_PERM is successful.\n");
 	}
 }
-- 
2.17.1

Re: [PATCH v4 2/2] selftests/x86/amx: Update the ARCH_REQ_XCOMP_PERM test

[Thomas Gleixner]

On Sat, Jan 29 2022 at 09:36, Chang S. Bae wrote:
> Update the arch_prctl test to check the permission bitmap whether the
> requested feature is added as expected or not.
>
> Every non-dynamic feature that is enabled is permitted already for use.
> TILECFG is not dynamic feature. Ensure the bit is always on from
> ARCH_GET_XCOMP_PERM.

Running it on a machine which does not have AMX results in:

 amx_64: [FAIL]	xstate cpuid: invalid tile data size/offset: 0/0: Success

It's not a failure, really. Selftests are supposed to run on all
machines and the proper thing to do if a hardware feature is not
available is to SKIP the test and return 0.

Thanks,

        tglx

Re: [PATCH v4 2/2] selftests/x86/amx: Update the ARCH_REQ_XCOMP_PERM test

[Chang S. Bae]

On 3/23/2022 9:44 AM, Thomas Gleixner wrote:
> 
> Running it on a machine which does not have AMX results in:
> 
>   amx_64: [FAIL]	xstate cpuid: invalid tile data size/offset: 0/0: Success
> 
> It's not a failure, really. Selftests are supposed to run on all
> machines and the proper thing to do if a hardware feature is not
> available is to SKIP the test and return 0.

Ah, right. The test should be just *skipped* on non-AMX or even 
non-XSAVE systems.

Will follow up with a separate patch.

Thanks,
Chang