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From:   Nitesh Lal <nilal@redhat.com>
Date:   Mon, 17 May 2021 17:13:18 -0400
Message-ID: <CAFki+L=RaSZXASAaAxBf=RJqXWju+pkSj3ftMkmoqCLPfg0v=g@mail.gmail.com>
Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when
 setting the hint
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        "frederic@kernel.org" <frederic@kernel.org>,
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On Mon, May 17, 2021 at 3:47 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Nitesh,
>
> On Mon, May 17 2021 at 14:21, Nitesh Lal wrote:
> > On Mon, May 17, 2021 at 1:26 PM Robin Murphy <robin.murphy@arm.com> wrote:
> >
> > We can use irq_set_affinity() to set the hint mask as well, however, maybe
> > there is a specific reason behind separating those two in the
> > first place (maybe not?).
>
> Yes, because kernel side settings might overwrite the hint.
>
> > But even in this case, we have to either modify the PMU drivers' IRQs
> > affinity from the userspace or we will have to make changes in the existing
> > request_irq code path.
>
> Adjusting them from user space does not work for various reasons,
> especially CPU hotplug.
>
> > I am not sure about the latter because we already have the required controls
> > to adjust the device IRQ mask (by using default_smp_affinity or by modifying
> > them manually).
>
> default_smp_affinity does not help at all and there is nothing a module
> can modify manually.

Right, it will not help a module.

>
> I'll send out a patch series which cleans that up soon.

Ack, thanks.

>
> Thanks,
>
>         tglx
>
>


--
Nitesh