Re: [PATCH] arm_mpam: Fix MPAM reset on resctrl unmount by clearing in_reset_state

[Zeng Heng <zengheng4@huawei.com>]

Hi Ben,

On 2026/2/27 22:16, Ben Horgan wrote:
> 
> 
> On 2/17/26 15:59, Ben Horgan wrote:
>> Hi Zeng,
>>
>> On 2/13/26 07:50, Zeng Heng wrote:
>>> When resctrl is unmounted, MPAM components should be reset to default
>>> configurations to avoid impacting system performance. However, after
>>> a user updates MPAM configuration via mpam_apply_config(), the
>>> in_reset_state flag remains true, causing mpam_reset_ris() to skip
>>> the actual register restoration on subsequent resets.
>>>
>>> For example, after mounting resctrl and modifying the root group's
>>> schemata (e.g., changing MBMAX/MBMIN values), unmounting resctrl
>>
>> nit: MBMIN isn't currently supported in resctrl. I'd just drop the
>> part in brackets.
>>
>>> would leave the modified MPAM settings in hardware registers since
>>> mpam_reset_ris() returns early due to in_reset_state still being true.
>>> This results in persistent performance restrictions even after resctrl
>>> is umounted.
>>>
>>> Fix by clearing in_reset_state to false immediately after successful
>>> configuration application, ensuring that the next reset operation
>>> properly restores MPAM register defaults.
>>>
>>> Fixes: f188a36ca241 ("arm_mpam: Reset MSC controls from cpuhp callbacks")
>>
>> mpam_apply_config() doesn't exist in this commit. I would have expected:
>> Fixes: 09b89d2a72f3 ("arm_mpam: Allow configuration to be applied and restored during cpu online")
>>
>>> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
>>
>> The change and justification looks good to me.
>>
>> Acked-by: Ben Horgan <ben.horgan@arm.com>
>>
> 
> I'll add this on to the start of the current mpam resctrl series as even
> though this is squashing an existing bug it can't be hit until mpam has
> a user interface and so doesn't need to go as a fix.
> 
> Thanks,
> 
> Ben
> 
> 
OK, get it.

Best regards,
Zeng Heng