Re: [PATCH v10 08/14] arm_mpam: propagate MSC access errors for interrupt control

[Andre Przywara]

Hi Ben,

On 9/11/26 16:26, Ben Horgan wrote:
> Hi Andre,
>
> On 11/09/2026 12:28, Andre Przywara wrote:
> > Allow the functions dealing with interrupt registration and enablement
> > to check for and return errors, and propagate MSC read and write errors
> > from the lower level up.
> > This does not cover the IRQ handler yet, as this needs some more
> > attention.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > Reviewed-by: Srivathsa L Rao <srivathsa.rao@xxxxxxxxxxxxxxxx>
>
> Commenting here as this is the last error propagation patch. I think we need a clean boundary for
> the error propagation. As you said a while back I think we can propagate error for all non-static
> functions from mpam_devices.c and the callers can discard the errors if appropriate. For instance,
> mpam_reset_class_locked() should propagate any error.

So I checked all non-static functions in mpam_devices.c: most either 
don't deal with MSCs at all, or already propagate errors.
The two outliers are mpam_disable(), which must be "void", due to it 
being called via DECLARE_WORK, and mpam_reset_class_locked(), as you 
write above. The latter is a bit sad, because the caller is void, so any 
errors would be discarded there anyway, but for the sake of completeness 
we should indeed propagate here.

And I guess it doesn't make sense to continue the vMSC or RIS list 
iterations after detecting the first error, but we just bail out 
immediately? Because any error would trigger mpam_disable() anyway?

Cheers,
Andre


> Thanks,
>
> Ben
>
> > ---
> >   drivers/resctrl/mpam_devices.c | 31 +++++++++++++++----------------
> >   1 file changed, 15 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> > index 558efab75f911..eb26c25b9f970 100644
> > --- a/drivers/resctrl/mpam_devices.c
> > +++ b/drivers/resctrl/mpam_devices.c
> > @@ -1105,7 +1105,9 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
> >   	}
> >   
> >   	/* Clear any stale errors */
> > -	mpam_msc_clear_esr(msc);
> > +	ret = mpam_msc_clear_esr(msc);
> > +	if (ret)
> > +		return ret;
> >   
> >   	spin_lock(&partid_max_lock);
> >   	mpam_partid_max = min(mpam_partid_max, msc->partid_max);
> > @@ -2668,9 +2670,7 @@ static int mpam_enable_msc_ecr(void *_msc)
> >   {
> >   	struct mpam_msc *msc = _msc;
> >   
> > -	__mpam_write_reg(msc, MPAMF_ECR, MPAMF_ECR_INTEN);
> > -
> > -	return 0;
> > +	return __mpam_write_reg(msc, MPAMF_ECR, MPAMF_ECR_INTEN);
> >   }
> >   
> >   /* This can run in mpam_disable(), and the interrupt handler on the same CPU */
> > @@ -2678,9 +2678,7 @@ static int mpam_disable_msc_ecr(void *_msc)
> >   {
> >   	struct mpam_msc *msc = _msc;
> >   
> > -	__mpam_write_reg(msc, MPAMF_ECR, 0);
> > -
> > -	return 0;
> > +	return __mpam_write_reg(msc, MPAMF_ECR, 0);
> >   }
> >   
> >   static irqreturn_t __mpam_irq_handler(int irq, struct mpam_msc *msc)
> > @@ -2777,11 +2775,13 @@ static int mpam_register_irqs(void)
> >   				return err;
> >   		}
> >   
> > -		mutex_lock(&msc->error_irq_lock);
> > -		msc->error_irq_req = true;
> > -		mpam_touch_msc(msc, mpam_enable_msc_ecr, msc);
> > -		msc->error_irq_hw_enabled = true;
> > -		mutex_unlock(&msc->error_irq_lock);
> > +		scoped_guard(mutex, &msc->error_irq_lock) {
> > +			msc->error_irq_req = true;
> > +			err = mpam_touch_msc(msc, mpam_enable_msc_ecr, msc);
> > +			if (err)
> > +				return err;
> > +			msc->error_irq_hw_enabled = true;
> > +		}
> >   	}
> >   
> >   	return 0;
> > @@ -2800,10 +2800,10 @@ static void mpam_unregister_irqs(void)
> >   		if (irq <= 0)
> >   			continue;
> >   
> > -		mutex_lock(&msc->error_irq_lock);
> > +		guard(mutex)(&msc->error_irq_lock);
> >   		if (msc->error_irq_hw_enabled) {
> > -			mpam_touch_msc(msc, mpam_disable_msc_ecr, msc);
> > -			msc->error_irq_hw_enabled = false;
> > +			if (!mpam_touch_msc(msc, mpam_disable_msc_ecr, msc))
> > +				msc->error_irq_hw_enabled = false;
> >   		}
> >   
> >   		if (msc->error_irq_req) {
> > @@ -2815,7 +2815,6 @@ static void mpam_unregister_irqs(void)
> >   			}
> >   			msc->error_irq_req = false;
> >   		}
> > -		mutex_unlock(&msc->error_irq_lock);
> >   	}
> >   }
> >