Re: [PATCH v14 25/32] fs/resctrl: Provide interface to update the event configurations

[Reinette Chatre]

Hi Babu,

On 6/30/25 5:43 PM, Moger, Babu wrote:
> On 6/25/2025 6:21 PM, Reinette Chatre wrote:
>> On 6/13/25 2:05 PM, Babu Moger wrote:

...

>>> +     * the assignment
>>> +     */
>>> +    list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
>>> +        rdtgroup_assign_cntr(r, prgrp, mevt);
>>> +
>>> +        list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list)
>>> +            rdtgroup_assign_cntr(r, crgrp, mevt);
>>> +    }
>>> +}
>>> +
>>> +static int resctrl_process_configs(char *tok, u32 *val)
>>> +{
>>> +    char *evt_str;
>>> +    u32 temp_val;
>>> +    bool found;
>>> +    int i;
>>> +
>>> +next_config:
>>> +    if (!tok || tok[0] == '\0')
>>> +        return 0;
>>> +
>>> +    /* Start processing the strings for each memory transaction type */
>>> +    evt_str = strim(strsep(&tok, ","));
>>> +    found = false;
>>> +    for (i = 0; i < NUM_MBM_EVT_VALUES; i++) {
>>> +        if (!strcmp(mbm_config_values[i].name, evt_str)) {
>>> +            temp_val = mbm_config_values[i].val;
>>> +            found = true;
>>> +            break;
>>> +        }
>>> +    }
>>> +
>>> +    if (!found) {
>>> +        rdt_last_cmd_printf("Invalid memory transaction type %s\n", evt_str);
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    *val |= temp_val;
>>
>> This still returns a partially initialized value on failure. Please only set
>> provided parameter on success.
> 
> Yes. Changed it.
> 
>  if (!tok || tok[0] == '\0') {
>                *val = temp_val;
>                return 0;
>  }

You may just not have included this in your snippet, but please ensure temp_val is always
initialized. Just this snippet on top of original patch risks using uninitialized variable.

>>> +
>>> +    goto next_config;
>>> +}
>>> +
>>> +static ssize_t event_filter_write(struct kernfs_open_file *of, char *buf,
>>> +                  size_t nbytes, loff_t off)
>>> +{
>>> +    struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>>> +    struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
>>
>> With mon_evt::rid available it should not be necessary to hardcode the resource?
> 
> changed it
> 
>  r = resctrl_arch_get_resource(mevt->rid);
> 
>> Do any of these new functions need a struct rdt_resource parameter in addition
>> to struct mon_evt?
> 
> We need to make a call resctrl_arch_mbm_cntr_assign_enabled(r)) to proceed. So we need  struct rdt_resource.

Understood, but since struct rdt_resource can be determined from mon_evt::rid
it is not obvious to me that providing both is always needed by all these functions.

Reinette