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

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Message-ID: <23667132-e070-437e-9d28-3db53ed220a5@amd.com>
Date: Tue, 1 Jul 2025 11:14:37 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, "Moger, Babu"
 <bmoger@....com>, corbet@....net, tony.luck@...el.com, Dave.Martin@....com,
 james.morse@....com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, akpm@...ux-foundation.org,
 rostedt@...dmis.org, paulmck@...nel.org, thuth@...hat.com, ardb@...nel.org,
 gregkh@...uxfoundation.org, seanjc@...gle.com, thomas.lendacky@....com,
 pawan.kumar.gupta@...ux.intel.com, manali.shukla@....com,
 perry.yuan@....com, kai.huang@...el.com, peterz@...radead.org,
 xiaoyao.li@...el.com, kan.liang@...ux.intel.com, mario.limonciello@....com,
 xin3.li@...el.com, gautham.shenoy@....com, xin@...or.com,
 chang.seok.bae@...el.com, fenghuay@...dia.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, eranian@...gle.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v14 25/32] fs/resctrl: Provide interface to update the
 event configurations

Hi Reinette,

On 6/30/25 20:33, Reinette Chatre wrote:
> 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.

Yes. Got it. Should have pasted the full change. Its taken care already.

> 
>>>> +
>>>> +    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.
> 
Yes. Got it. Taken care of this.
-- 
Thanks
Babu Moger