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 <ilpo.jarvi...@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.cha...@intel.com>
---
Changes since V1:
- New patch
---
 tools/testing/selftests/resctrl/fill_buf.c      |  7 ++++---
 tools/testing/selftests/resctrl/resctrl.h       |  2 +-
 tools/testing/selftests/resctrl/resctrl_tests.c |  8 +++++++-
 tools/testing/selftests/resctrl/resctrl_val.c   | 11 +----------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/resctrl/fill_buf.c 
b/tools/testing/selftests/resctrl/fill_buf.c
index 34e5df721430..854f0108d8e6 100644
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/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;
diff --git a/tools/testing/selftests/resctrl/resctrl.h 
b/tools/testing/selftests/resctrl/resctrl.h
index 2dda56084588..51f5f4b25e06 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/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,
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c 
b/tools/testing/selftests/resctrl/resctrl_tests.c
index ecbb7605a981..bee4123a5a9b 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -266,7 +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";
+               /*
+                * 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;
                uparams.benchmark_cmd[5] = NULL;
        }
 
diff --git a/tools/testing/selftests/resctrl/resctrl_val.c 
b/tools/testing/selftests/resctrl/resctrl_val.c
index e88d5ca30517..5331354aaf64 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/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 */
-- 
2.46.0


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