selftests/resctrl: Don't hard code value of "no_of_bits" variable

Cache related tests (like CAT and CMT) depend on a variable called
no_of_bits to run. no_of_bits defines the number of contiguous bits
that should be set in the CBM mask and a user can pass a value for
no_of_bits using -n command line argument. If a user hasn't passed any
value, it defaults to 5 (randomly chosen value).

Hard coding no_of_bits to 5 will make the cache tests fail to run on
systems that support maximum cbm mask that is less than or equal to 5 bits.
Hence, don't hard code no_of_bits value.

If a user passes a value for "no_of_bits" using -n option, use it.
Otherwise, no_of_bits is equal to half of the maximum number of bits in
the cbm mask.

Please note that CMT test is still hard coded to 5 bits. It will change in
subsequent patches that change CMT test.
Tested-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/resctrl/cat_test.c

@@ -130,7 +130,10 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	/* Get max number of bits from default-cabm mask */
 	count_of_bits = count_bits(long_mask);
 
-	if (n < 1 || n > count_of_bits - 1) {
+	if (!n)
+		n = count_of_bits / 2;
+
+	if (n > count_of_bits - 1) {
 		ksft_print_msg("Invalid input value for no_of_bits n!\n");
 		ksft_print_msg("Please enter value in range 1 to %d\n",
 			       count_of_bits - 1);

tools/testing/selftests/resctrl/resctrl_tests.c

@@ -57,7 +57,7 @@ void tests_cleanup(void)
 int main(int argc, char **argv)
 {
 	bool has_ben = false, mbm_test = true, mba_test = true, cmt_test = true;
-	int res, c, cpu_no = 1, span = 250, argc_new = argc, i, no_of_bits = 5;
+	int res, c, cpu_no = 1, span = 250, argc_new = argc, i, no_of_bits = 0;
 	char *benchmark_cmd[BENCHMARK_ARGS], bw_report[64], bm_type[64];
 	char benchmark_cmd_area[BENCHMARK_ARGS][BENCHMARK_ARG_SIZE];
 	int ben_ind, ben_count, tests = 0;
@@ -110,6 +110,10 @@ int main(int argc, char **argv)
 			break;
 		case 'n':
 			no_of_bits = atoi(optarg);
+			if (no_of_bits <= 0) {
+				printf("Bail out! invalid argument for no_of_bits\n");
+				return -1;
+			}
 			break;
 		case 'h':
 			cmd_help();
@@ -188,7 +192,7 @@ int main(int argc, char **argv)
 		ksft_print_msg("Starting CMT test ...\n");
 		if (!has_ben)
 			sprintf(benchmark_cmd[5], "%s", CMT_STR);
-		res = cmt_resctrl_val(cpu_no, no_of_bits, benchmark_cmd);
+		res = cmt_resctrl_val(cpu_no, 5, benchmark_cmd);
 		ksft_test_result(!res, "CMT: test\n");
 		cmt_test_cleanup();
 	}