Within mba_setup() the programmed bandwidth delay value starts at the maximum (100, or rather ALLOCATION_MAX) and progresses towards ALLOCATION_MIN by decrementing with ALLOCATION_STEP.
The programmed bandwidth delay should never be negative, so representing it with an unsigned int is most appropriate. This may introduce confusion because of the "allocation > ALLOCATION_MAX" check used to check wraparound of the subtraction.
Modify the mba_setup() flow to start at the minimum, ALLOCATION_MIN, and incrementally, with ALLOCATION_STEP steps, adjust the bandwidth delay value. This avoids wraparound while making the purpose of "allocation > ALLOCATION_MAX" clear and eliminates the need for the "allocation < ALLOCATION_MIN" check.
Reported-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Closes: https://lore.kernel.org/lkml/1903ac13-5c9c-ef8d-78e0-417ac34a971b@linux.inte... Signed-off-by: Reinette Chatre reinette.chatre@intel.com Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com --- Changes since V1: - New patch - Add Ilpo's Reviewed-by tag. --- tools/testing/selftests/resctrl/mba_test.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c index ab8496a4925b..da40a8ed4413 100644 --- a/tools/testing/selftests/resctrl/mba_test.c +++ b/tools/testing/selftests/resctrl/mba_test.c @@ -39,7 +39,8 @@ static int mba_setup(const struct resctrl_test *test, const struct user_params *uparams, struct resctrl_val_param *p) { - static int runs_per_allocation, allocation = 100; + static unsigned int allocation = ALLOCATION_MIN; + static int runs_per_allocation; char allocation_str[64]; int ret;
@@ -50,7 +51,7 @@ static int mba_setup(const struct resctrl_test *test, if (runs_per_allocation++ != 0) return 0;
- if (allocation < ALLOCATION_MIN || allocation > ALLOCATION_MAX) + if (allocation > ALLOCATION_MAX) return END_OF_TESTS;
sprintf(allocation_str, "%d", allocation); @@ -59,7 +60,7 @@ static int mba_setup(const struct resctrl_test *test, if (ret < 0) return ret;
- allocation -= ALLOCATION_STEP; + allocation += ALLOCATION_STEP;
return 0; } @@ -72,8 +73,9 @@ static int mba_measure(const struct user_params *uparams,
static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc) { - int allocation, runs; + unsigned int allocation; bool ret = false; + int runs;
ksft_print_msg("Results are displayed in (MB)\n"); /* Memory bandwidth from 100% down to 10% */ @@ -103,7 +105,7 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc) avg_diff_per > MAX_DIFF_PERCENT ? "Fail:" : "Pass:", MAX_DIFF_PERCENT, - ALLOCATION_MAX - ALLOCATION_STEP * allocation); + ALLOCATION_MIN + ALLOCATION_STEP * allocation);
ksft_print_msg("avg_diff_per: %d%%\n", avg_diff_per); ksft_print_msg("avg_bw_imc: %lu\n", avg_bw_imc);