Re: [RFC PATCH 24/36] arm_mpam: Extend reset logic to allow devices to be reset any time

[James Morse]

Hi Ben,

On 28/07/2025 11:22, Ben Horgan wrote:
> On 7/11/25 19:36, James Morse 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.
> > diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/
> > mpam_devices.c
> > index 2e32e54cc081..145535cd4732 100644
> > --- a/drivers/platform/arm64/mpam/mpam_devices.c
> > +++ b/drivers/platform/arm64/mpam/mpam_devices.c

> > +/*
> > + * Called in response to an error IRQ.
> > + * All of MPAMs errors indicate a software bug, restore any modified
> > + * controls to their reset values.
> > + */
> > +void mpam_disable(void)
> > +{
> > +    int idx;
> > +    struct mpam_class *class;
> > +
> > +    idx = srcu_read_lock(&mpam_srcu);
> > +    list_for_each_entry_srcu(class, &mpam_classes, classes_list,
> > +                 srcu_read_lock_held(&mpam_srcu))
> > +        mpam_reset_class(class);
> > +    srcu_read_unlock(&mpam_srcu, idx);
> > +}
> Consider moving to the next patch where you introduce interrupt support.

I pulled these changes out of that patch to try and make it simpler!
Doing that would leave a bunch of static functions unused.


Thanks,

James