selftests/resctrl: Remove "once" parameter required to be false

The CMT, MBM, and MBA tests rely on a benchmark that runs while
the test makes changes to needed configuration (for example memory
bandwidth allocation) and takes needed measurements. By default
the "fill_buf" benchmark is used and by default (via its
"once = false" setting) "fill_buf" is configured to run until
terminated after the test completes.

An unintended consequence of enabling the user to override the
benchmark also enables the user to change parameters to the
"fill_buf" benchmark. This enables the user to set "fill_buf" to
only cycle through the buffer once (by setting "once = true")
and thus breaking the CMT, MBA, and MBM tests that expect
workload/interference to be reflected by their measurements.

Prevent user space from changing the "once" parameter and ensure
that it is always false for the CMT, MBA, and MBM tests.

Suggested-by: Ilpo Järvinen <[email protected]>
Signed-off-by: Reinette Chatre <[email protected]>
Reviewed-by: Ilpo Järvinen <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: rchatre

tools/testing/selftests/resctrl/fill_buf.c

@@ -151,7 +151,7 @@ unsigned char *alloc_buffer(size_t buf_size, int memflush)
 	return buf;
 }
 
-int run_fill_buf(size_t buf_size, int memflush, int op, bool once)
+int run_fill_buf(size_t buf_size, int memflush, int op)
 {
 	unsigned char *buf;
 
@@ -160,9 +160,10 @@ int run_fill_buf(size_t buf_size, int memflush, int op, bool once)
 		return -1;
 
 	if (op == 0)
-		fill_cache_read(buf, buf_size, once);
+		fill_cache_read(buf, buf_size, false);
 	else
-		fill_cache_write(buf, buf_size, once);
+		fill_cache_write(buf, buf_size, false);
+
 	free(buf);
 
 	return 0;

tools/testing/selftests/resctrl/resctrl.h

@@ -142,7 +142,7 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu,
 unsigned char *alloc_buffer(size_t buf_size, int memflush);
 void mem_flush(unsigned char *buf, size_t buf_size);
 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 run_fill_buf(size_t buf_size, int memflush, int op);
 int initialize_mem_bw_imc(void);
 int measure_mem_bw(const struct user_params *uparams,
 		   struct resctrl_val_param *param, pid_t bm_pid,

tools/testing/selftests/resctrl/resctrl_tests.c

@@ -266,8 +266,13 @@ int main(int argc, char **argv)
 		uparams.benchmark_cmd[1] = span_str;
 		uparams.benchmark_cmd[2] = "1";
 		uparams.benchmark_cmd[3] = "0";
-		uparams.benchmark_cmd[4] = "false";
-		uparams.benchmark_cmd[5] = NULL;
+		/*
+		 * Fourth parameter was previously used to indicate
+		 * how long "fill_buf" should run for, with "false"
+		 * ("fill_buf" will keep running until terminated)
+		 * the only option that works.
+		 */
+		uparams.benchmark_cmd[4] = NULL;
 	}
 
 	ksft_set_plan(tests);

tools/testing/selftests/resctrl/resctrl_val.c

@@ -625,7 +625,6 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
 	int operation, ret, memflush;
 	char **benchmark_cmd;
 	size_t span;
-	bool once;
 	FILE *fp;
 
 	benchmark_cmd = info->si_ptr;
@@ -645,16 +644,8 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
 		span = strtoul(benchmark_cmd[1], NULL, 10);
 		memflush =  atoi(benchmark_cmd[2]);
 		operation = atoi(benchmark_cmd[3]);
-		if (!strcmp(benchmark_cmd[4], "true")) {
-			once = true;
-		} else if (!strcmp(benchmark_cmd[4], "false")) {
-			once = false;
-		} else {
-			ksft_print_msg("Invalid once parameter\n");
-			parent_exit(ppid);
-		}
 
-		if (run_fill_buf(span, memflush, operation, once))
+		if (run_fill_buf(span, memflush, operation))
 			fprintf(stderr, "Error in running fill buffer\n");
 	} else {
 		/* Execute specified benchmark */