Re: [RESEND PATCH v4 08/15] fs/resctrl: Add interface to display supported and active kernel-mode policy

[Babu Moger <babu.moger@amd.com>]

Hi Reinette,

On 8/12/26 18:38, Reinette Chatre wrote:
> Hi Babu,
> 
> On 8/12/26 3:57 PM, Moger, Babu wrote:
>> On 8/10/2026 10:18 PM, Reinette Chatre wrote:
>>> On 7/7/26 2:50 PM, Babu Moger wrote:
> 
> ...
> 
>>>> +         */
>>>> +        rdtgrp = resctrl_kcfg.k_rdtgrp;
>>>> +        if (!rdtgrp) {
>>>> +            ret = -ENOENT;
>>>> +            goto out_unlock;
>>>
>>> If this fails there needs to be content in last_cmd_status. Otherwise this
>>> fails and then last_cmd_status reads "ok" or worse .. an old failure message.
>>
>> if (WARN_ON(!rdtgrp)) {
>>      rdt_last_cmd_puts("Invalid kernel mode group\n");
>>      ret = -ENOENT;
>>      goto out_unlock;
>> }
> It is not clear to me why the WARN_ON() was added. Is the resource group not being
> associated with kernel mode not a legitimate scenario if the kernel mode group was
> re-assigned while the reader of this file was blocked on the mutex?
> 
A valid group is required whenever any global mode is enabled. Reaching 
this condition without one is unexpected and should be treated as a bug.

To help catch this, I added a WARN_ON() to log the issue. I think 
updating last_cmd_status is reasonable as well and should provide the 
necessary user-visible error indication.

thanks
Babu