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From:   Nitesh Lal <nilal@redhat.com>
Date:   Thu, 17 Jun 2021 15:34:18 -0400
Message-ID: <CAFki+LkTqThGZDGui4N6Ko-Z8PMPtX7m-KPm0BM4SvbAxrOqVw@mail.gmail.com>
Subject: Re: [PATCH v1 04/14] scsi: megaraid_sas: Use irq_set_affinity_and_hint
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Nitesh Narayan Lal <nitesh@redhat.com>,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
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On Thu, Jun 17, 2021 at 3:31 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2021-06-17 19:22, Nitesh Narayan Lal wrote:
> > The driver uses irq_set_affinity_hint() specifically for the high IOPS
> > queue interrupts for two purposes:
> >
> > - To set the affinity_hint which is consumed by the userspace for
> >    distributing the interrupts
> >
> > - To apply an affinity that it provides
> >
> > The driver enforces its own affinity to bind the high IOPS queue interrupts
> > to the local NUMA node. However, irq_set_affinity_hint() applying the
> > provided cpumask as an affinity for the interrupt is an undocumented side
> > effect.
> >
> > To remove this side effect irq_set_affinity_hint() has been marked
> > as deprecated and new interfaces have been introduced. Hence, replace the
> > irq_set_affinity_hint() with the new interface irq_set_affinity_and_hint()
> > that clearly indicates the purpose of the usage and is meant to apply the
> > affinity and set the affinity_hint pointer. Also, replace
> > irq_set_affinity_hint() with irq_update_affinity_hint() when only
> > affinity_hint needs to be updated.
> >
> > Change the megasas_set_high_iops_queue_affinity_hint function name to
> > megasas_set_high_iops_queue_affinity_and_hint to clearly indicate that the
> > function is setting both affinity and affinity_hint.
> >
> > Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
> > ---
> >   drivers/scsi/megaraid/megaraid_sas_base.c | 25 ++++++++++++++---------
> >   1 file changed, 15 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
> > index 4d4e9dbe5193..54f4eac09589 100644
> > --- a/drivers/scsi/megaraid/megaraid_sas_base.c
> > +++ b/drivers/scsi/megaraid/megaraid_sas_base.c
> > @@ -5666,7 +5666,7 @@ megasas_setup_irqs_msix(struct megasas_instance *instance, u8 is_probe)
> >                               "Failed to register IRQ for vector %d.\n", i);
> >                       for (j = 0; j < i; j++) {
> >                               if (j < instance->low_latency_index_start)
> > -                                     irq_set_affinity_hint(
> > +                                     irq_update_affinity_hint(
> >                                               pci_irq_vector(pdev, j), NULL);
> >                               free_irq(pci_irq_vector(pdev, j),
> >                                        &instance->irq_context[j]);
> > @@ -5709,7 +5709,7 @@ megasas_destroy_irqs(struct megasas_instance *instance) {
> >       if (instance->msix_vectors)
> >               for (i = 0; i < instance->msix_vectors; i++) {
> >                       if (i < instance->low_latency_index_start)
> > -                             irq_set_affinity_hint(
> > +                             irq_update_affinity_hint(
> >                                   pci_irq_vector(instance->pdev, i), NULL);
> >                       free_irq(pci_irq_vector(instance->pdev, i),
> >                                &instance->irq_context[i]);
> > @@ -5840,22 +5840,27 @@ int megasas_get_device_list(struct megasas_instance *instance)
> >   }
> >
> >   /**
> > - * megasas_set_high_iops_queue_affinity_hint -       Set affinity hint for high IOPS queues
> > - * @instance:                                        Adapter soft state
> > - * return:                                   void
> > + * megasas_set_high_iops_queue_affinity_and_hint -   Set affinity and hint
> > + *                                                   for high IOPS queues
> > + * @instance:                                                Adapter soft state
> > + * return:                                           void
> >    */
> >   static inline void
> > -megasas_set_high_iops_queue_affinity_hint(struct megasas_instance *instance)
> > +megasas_set_high_iops_queue_affinity_and_hint(struct megasas_instance *instance)
> >   {
> >       int i;
> > +     unsigned int irq;
> >       int local_numa_node;
> > +     const struct cpumask *mask;
> >
> >       if (instance->perf_mode == MR_BALANCED_PERF_MODE) {
> >               local_numa_node = dev_to_node(&instance->pdev->dev);
>
> Drive-by nit: you could assign mask in this scope.
>

Sure

> > -             for (i = 0; i < instance->low_latency_index_start; i++)
> > -                     irq_set_affinity_hint(pci_irq_vector(instance->pdev, i),
> > -                             cpumask_of_node(local_numa_node));
> > +             for (i = 0; i < instance->low_latency_index_start; i++) {
> > +                     irq = pci_irq_vector(instance->pdev, i);
> > +                     mask = cpumask_of_node(local_numa_node);
> > +                     irq_update_affinity_hint(irq, mask);
>
> And this doesn't seem to match what the commit message says?
>

Clearly, thanks for catching it.
This should be irq_set_affinity_and_hint().

> Robin.
>
> > +             }
> >       }
> >   }
> >
> > @@ -5944,7 +5949,7 @@ megasas_alloc_irq_vectors(struct megasas_instance *instance)
> >               instance->msix_vectors = 0;
> >
> >       if (instance->smp_affinity_enable)
> > -             megasas_set_high_iops_queue_affinity_hint(instance);
> > +             megasas_set_high_iops_queue_affinity_and_hint(instance);
> >   }
> >
> >   /**
> >
>


-- 
Thanks
Nitesh