selftests/resctrl: Skip the test if requested resctrl feature is not supported

There could be two reasons why a resctrl feature might not be enabled on
the platform
1. H/W might not support the feature
2. Even if the H/W supports it, the user might have disabled the feature
through kernel command line arguments

Hence, any resctrl unit test (like cmt, cat, mbm and mba) before starting
the test will first check if the feature is enabled on the platform or not.
If the feature isn't enabled, then the test returns with an error status.
For example, if MBA isn't supported on a platform and if the user tries to
run MBA, the output will look like this

ok mounting resctrl to "/sys/fs/resctrl"
not ok MBA: schemata change

But, not supporting a feature isn't a test failure. So, instead of treating
it as an error, use the SKIP directive of the TAP protocol. With the
change, the output will look as below

ok MBA # SKIP Hardware does not support MBA or MBA is disabled

Suggested-by: Reinette Chatre <[e-mail]>
Tested-by: Babu Moger <[e-mail]>
Signed-off-by: Fenghua Yu <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/resctrl/cat_test.c

···
 	if (ret)
 		return ret;
 
-	if (!validate_resctrl_feature_request("cat"))
-		return -1;
-
 	/* Get default cbm mask for L3/L2 cache */
 	ret = get_cbm_mask(cache_type, cbm_mask);
 	if (ret)

tools/testing/selftests/resctrl/mba_test.c

···
 
 	remove(RESULT_FILE_NAME);
 
-	if (!validate_resctrl_feature_request("mba"))
-		return -1;
-
 	ret = resctrl_val(benchmark_cmd, &param);
 	if (ret)
 		return ret;

tools/testing/selftests/resctrl/mbm_test.c

···
 
 	remove(RESULT_FILE_NAME);
 
-	if (!validate_resctrl_feature_request("mbm"))
-		return -1;
-
 	ret = resctrl_val(benchmark_cmd, &param);
 	if (ret)
 		return ret;

tools/testing/selftests/resctrl/resctrl_tests.c

···
 	int res;
 
 	ksft_print_msg("Starting MBM BW change ...\n");
+
+	if (!validate_resctrl_feature_request(MBM_STR)) {
+		ksft_test_result_skip("Hardware does not support MBM or MBM is disabled\n");
+		return;
+	}
+
 	if (!has_ben)
 		sprintf(benchmark_cmd[5], "%s", MBA_STR);
 	res = mbm_bw_change(span, cpu_no, bw_report, benchmark_cmd);
···
 	int res;
 
 	ksft_print_msg("Starting MBA Schemata change ...\n");
+
+	if (!validate_resctrl_feature_request(MBA_STR)) {
+		ksft_test_result_skip("Hardware does not support MBA or MBA is disabled\n");
+		return;
+	}
+
 	if (!has_ben)
 		sprintf(benchmark_cmd[1], "%d", span);
 	res = mba_schemata_change(cpu_no, bw_report, benchmark_cmd);
···
 	int res;
 
 	ksft_print_msg("Starting CMT test ...\n");
+	if (!validate_resctrl_feature_request(CMT_STR)) {
+		ksft_test_result_skip("Hardware does not support CMT or CMT is disabled\n");
+		return;
+	}
+
 	if (!has_ben)
 		sprintf(benchmark_cmd[5], "%s", CMT_STR);
 	res = cmt_resctrl_val(cpu_no, 5, benchmark_cmd);
···
 	int res;
 
 	ksft_print_msg("Starting CAT test ...\n");
+
+	if (!validate_resctrl_feature_request(CAT_STR)) {
+		ksft_test_result_skip("Hardware does not support CAT or CAT is disabled\n");
+		return;
+	}
+
 	res = cat_perf_miss_val(cpu_no, no_of_bits, "L3");
 	ksft_test_result(!res, "CAT: test\n");
 	cat_test_cleanup();