selftests/resctrl: Simplify bandwidth report type handling

bw_report is only needed for selecting the correct value from the
values IMC measured. It is a member in the resctrl_val_param struct and
is always set to "reads". The value is then checked in resctrl_val()
using validate_bw_report_request() that besides validating the input,
assumes it can mutate the string which is questionable programming
practice.

Simplify handling bw_report:

- Convert validate_bw_report_request() into get_bw_report_type() that
  inputs and returns const char *. Use NULL to indicate error.

- Validate the report types inside measure_mem_bw(), not in
  resctrl_val().

- Pass bw_report to measure_mem_bw() from ->measure() hook because
  resctrl_val() no longer needs bw_report for anything.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/resctrl/mba_test.c

@@ -67,7 +67,7 @@ static int mba_setup(const struct resctrl_test *test,
 static int mba_measure(const struct user_params *uparams,
 		       struct resctrl_val_param *param, pid_t bm_pid)
 {
-	return measure_mem_bw(uparams, param, bm_pid);
+	return measure_mem_bw(uparams, param, bm_pid, "reads");
 }
 
 static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
@@ -168,7 +168,6 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param
 		.ctrlgrp	= "c1",
 		.mongrp		= "m1",
 		.filename	= RESULT_FILE_NAME,
-		.bw_report	= "reads",
 		.init		= mba_init,
 		.setup		= mba_setup,
 		.measure	= mba_measure,

tools/testing/selftests/resctrl/mbm_test.c

@@ -121,7 +121,7 @@ static int mbm_setup(const struct resctrl_test *test,
 static int mbm_measure(const struct user_params *uparams,
 		       struct resctrl_val_param *param, pid_t bm_pid)
 {
-	return measure_mem_bw(uparams, param, bm_pid);
+	return measure_mem_bw(uparams, param, bm_pid, "reads");
 }
 
 static void mbm_test_cleanup(void)
@@ -135,7 +135,6 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param
 		.resctrl_val	= MBM_STR,
 		.ctrlgrp	= "c1",
 		.filename	= RESULT_FILE_NAME,
-		.bw_report	= "reads",
 		.init		= mbm_init,
 		.setup		= mbm_setup,
 		.measure	= mbm_measure,

tools/testing/selftests/resctrl/resctrl.h

@@ -85,7 +85,6 @@ struct resctrl_test {
  * @ctrlgrp:		Name of the control monitor group (con_mon grp)
  * @mongrp:		Name of the monitor group (mon grp)
  * @filename:		Name of file to which the o/p should be written
- * @bw_report:		Bandwidth report type (reads vs writes)
  * @init:		Callback function to initialize test environment
  * @setup:		Callback function to setup per test run environment
  * @measure:		Callback that performs the measurement (a single test)
@@ -95,7 +94,6 @@ struct resctrl_val_param {
 	char		ctrlgrp[64];
 	char		mongrp[64];
 	char		filename[64];
-	char		*bw_report;
 	unsigned long	mask;
 	int		num_of_runs;
 	int		(*init)(const struct resctrl_val_param *param,
@@ -135,7 +133,7 @@ int filter_dmesg(void);
 int get_domain_id(const char *resource, int cpu_no, int *domain_id);
 int mount_resctrlfs(void);
 int umount_resctrlfs(void);
-int validate_bw_report_request(char *bw_report);
+const char *get_bw_report_type(const char *bw_report);
 bool resctrl_resource_exists(const char *resource);
 bool resctrl_mon_feature_exists(const char *resource, const char *feature);
 bool resource_info_file_exists(const char *resource, const char *file);
@@ -154,7 +152,8 @@ void fill_cache_read(unsigned char *buf, size_t buf_size, bool once);
 int run_fill_buf(size_t buf_size, int memflush, int op, bool once);
 int initialize_mem_bw_imc(void);
 int measure_mem_bw(const struct user_params *uparams,
-		   struct resctrl_val_param *param, pid_t bm_pid);
+		   struct resctrl_val_param *param, pid_t bm_pid,
+		   const char *bw_report);
 void initialize_mem_bw_resctrl(const struct resctrl_val_param *param,
 			       int domain_id);
 int resctrl_val(const struct resctrl_test *test,

tools/testing/selftests/resctrl/resctrl_val.c

@@ -349,7 +349,7 @@ static void do_imc_mem_bw_test(void)
  *
  * Return: = 0 on success. < 0 on failure.
  */
-static int get_mem_bw_imc(char *bw_report, float *bw_imc)
+static int get_mem_bw_imc(const char *bw_report, float *bw_imc)
 {
 	float reads, writes, of_mul_read, of_mul_write;
 	int imc;
@@ -556,6 +556,7 @@ static int print_results_bw(char *filename, pid_t bm_pid, float bw_imc,
  * @uparams:		User supplied parameters
  * @param:		Parameters passed to resctrl_val()
  * @bm_pid:		PID that runs the benchmark
+ * @bw_report:		Bandwidth report type (reads, writes)
  *
  * Measure memory bandwidth from resctrl and from another source which is
  * perf imc value or could be something else if perf imc event is not
@@ -563,13 +564,18 @@ static int print_results_bw(char *filename, pid_t bm_pid, float bw_imc,
  * 1 sec to measure the data.
  */
 int measure_mem_bw(const struct user_params *uparams,
-		   struct resctrl_val_param *param, pid_t bm_pid)
+		   struct resctrl_val_param *param, pid_t bm_pid,
+		   const char *bw_report)
 {
 	unsigned long bw_resc, bw_resc_start, bw_resc_end;
 	FILE *mem_bw_fp;
 	float bw_imc;
 	int ret;
 
+	bw_report = get_bw_report_type(bw_report);
+	if (!bw_report)
+		return -1;
+
 	mem_bw_fp = open_mem_bw_resctrl(mbm_total_path);
 	if (!mem_bw_fp)
 		return -1;
@@ -590,7 +596,7 @@ int measure_mem_bw(const struct user_params *uparams,
 	if (ret < 0)
 		goto close_imc;
 
-	ret = get_mem_bw_imc(param->bw_report, &bw_imc);
+	ret = get_mem_bw_imc(bw_report, &bw_imc);
 	if (ret < 0)
 		goto close_imc;
 
@@ -694,13 +700,6 @@ int resctrl_val(const struct resctrl_test *test,
 		return ret;
 	}
 
-	if (!strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR)) ||
-	    !strncmp(resctrl_val, MBM_STR, sizeof(MBM_STR))) {
-		ret = validate_bw_report_request(param->bw_report);
-		if (ret)
-			return ret;
-	}
-
 	/*
 	 * If benchmark wasn't successfully started by child, then child should
 	 * kill parent, so save parent's pid

tools/testing/selftests/resctrl/resctrlfs.c

@@ -837,22 +837,21 @@ int filter_dmesg(void)
 	return 0;
 }
 
-int validate_bw_report_request(char *bw_report)
+const char *get_bw_report_type(const char *bw_report)
 {
 	if (strcmp(bw_report, "reads") == 0)
-		return 0;
+		return bw_report;
 	if (strcmp(bw_report, "writes") == 0)
-		return 0;
+		return bw_report;
 	if (strcmp(bw_report, "nt-writes") == 0) {
-		strcpy(bw_report, "writes");
-		return 0;
+		return "writes";
 	}
 	if (strcmp(bw_report, "total") == 0)
-		return 0;
+		return bw_report;
 
 	fprintf(stderr, "Requested iMC bandwidth report type unavailable\n");
 
-	return -1;
+	return NULL;
 }
 
 int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu,