Re: [PATCH v2 17/29] arm_mpam: Extend reset logic to allow devices to be reset any time

[James Morse]

Hi Jonathan,

On 12/09/2025 13:02, Jonathan Cameron wrote:
> On Wed, 10 Sep 2025 20:42:57 +0000
> James Morse <james.morse@xxxxxxx> wrote:
> 
>> cpuhp callbacks aren't the only time the MSC configuration may need to
>> be reset. Resctrl has an API call to reset a class.
>> If an MPAM error interrupt arrives it indicates the driver has
>> misprogrammed an MSC. The safest thing to do is reset all the MSCs
>> and disable MPAM.
>>
>> Add a helper to reset RIS via their class. Call this from mpam_disable(),
>> which can be scheduled from the error interrupt handler.

>> Changes since v1:
>>  * Use guard macro for srcu.
> 
> I'm not seeing a strong reason for doing this for the case here and not
> for cases in earlier patches like in mpam_cpu_online() 

I just missed them...


> I'm a fan of using
> these broadly in a given code base, so would guard(srcu) in those earlier patches
> as well.

I've done the online/offline - I'll take another pass through them.


> Anyhow, one other trivial thing inline that you can ignore or not as you wish.
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>

Thanks!

>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index e7faf453b5d7..a9d3c4b09976 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c

>> @@ -1340,8 +1338,56 @@ static void mpam_enable_once(void)
>> +static void mpam_reset_component_locked(struct mpam_component *comp)
>> +{
>> +	struct mpam_msc *msc;
>> +	struct mpam_vmsc *vmsc;
>> +	struct mpam_msc_ris *ris;
>> +
>> +	lockdep_assert_cpus_held();
>> +
>> +	guard(srcu)(&mpam_srcu);
>> +	list_for_each_entry_srcu(vmsc, &comp->vmsc, comp_list,
>> +				 srcu_read_lock_held(&mpam_srcu)) {
>> +		msc = vmsc->msc;
> 
> Might be worth reducing scope of msc and ris

Sure,


Thanks,

James