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>>>> + struct rdt_resource *r; >>>> + u32 evt_cfg = 0; >>>> + int ret = 0; >>>> + >>>> + /* Valid input requires a trailing newline */ >>>> + if (nbytes == 0 || buf[nbytes - 1] != '\n') >>>> + return -EINVAL; >>>> + >>>> + buf[nbytes - 1] = '\0'; >>>> + >>>> + cpus_read_lock(); >>>> + mutex_lock(&rdtgroup_mutex); >>>> + >>>> + rdt_last_cmd_clear(); >>>> + >>>> + r = resctrl_arch_get_resource(mevt->rid); >>>> + if (!resctrl_arch_mbm_cntr_assign_enabled(r)) { >>>> + rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n"); >>>> + ret = -EINVAL; >>>> + goto out_unlock; >>>> + } >>>> + >>>> + ret = resctrl_parse_mem_transactions(buf, &evt_cfg); >>>> + if (!ret && mevt->evt_cfg != evt_cfg) { >>> >>> ... is evt_cfg of 0 (a) a valid value (that will not cause hardware to fault) and >>> (b) a reasonable value to allow? >>> >> >> The value evt_cfg = 0 is valid and permitted for both ABMC and BMEC. I >> have confirmed here through verification and testing. In that case, the >> event counter will not be monitoring anything. > > Thank you for checking. > > I do not know what a use case for this would be but I also do not see why kernel > should prevent user space from doing this. Looks like event_filter_show() will then > just print a '\n' that is expected. Are counters expected to always return 0 in this > case or will they return an error? I am not clear on what qualifies as "invalid counter > configuration" for ABMC that results in RMID_VAL_ERROR. The event counters return 0 in this case. I would not think this as an invalid event configuration. One option is to add a text in last_cmd_status from event_filter_show(). rdt_last_cmd_printf("Event %s is not configured to monitor any memory transactions\n", mevt->name); -- Thanks Babu Moger