Commit 20d96b25cc4c ("selftests/resctrl: Fix schemata write error check") exposed a problem in feature detection logic in MBM selftest. If schemata does not support MB:x=x entries, the schemata write to initialize 100% memory bandwidth allocation in mbm_setup() will now fail with -EINVAL due to the error handling corrected by the commit 20d96b25cc4c ("selftests/resctrl: Fix schemata write error check"). That commit just uncovers the failed write, it is not wrong itself.

If MB:x=x is not supported by schemata, it is safe to assume 100% memory bandwidth is always set. Therefore, the previously ignored error does not make the MBM test itself wrong.

Restore the previous behavior of MBM test by checking MB support before attempting to write it into schemata which results in behavior equivalent to ignoring the write error.

Fixes: 20d96b25cc4c ("selftests/resctrl: Fix schemata write error check") Signed-off-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Reviewed-by: Reinette Chatre reinette.chatre@intel.com --- tools/testing/selftests/resctrl/mbm_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c index d3c0d30c676a..741533f2b075 100644 --- a/tools/testing/selftests/resctrl/mbm_test.c +++ b/tools/testing/selftests/resctrl/mbm_test.c @@ -95,7 +95,7 @@ static int mbm_setup(struct resctrl_val_param *p) return END_OF_TESTS;

/* Set up shemata with 100% allocation on the first run. */ - if (p->num_of_runs == 0) + if (p->num_of_runs == 0 && validate_resctrl_feature_request("MB", NULL)) ret = write_schemata(p->ctrlgrp, "100", p->cpu_no, p->resctrl_val);