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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Nitesh Lal <nilal@redhat.com>, Robin Murphy <robin.murphy@arm.com>
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        Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint
In-Reply-To: <CAFki+L=LDizBJmFUieMDg9J=U6mn6XxTPPkAaWiyppTouTzaqw@mail.gmail.com>
References: <20210501021832.743094-1-jesse.brandeburg@intel.com> <16d8ca67-30c6-bb4b-8946-79de8629156e@arm.com> <20210504092340.00006c61@intel.com> <CAFki+LmR-o+Fng21ggy48FUX7RhjjpjO87dn3Ld+L4BK2pSRZg@mail.gmail.com> <bf1d4892-0639-0bbf-443e-ba284a8ed457@arm.com> <CAFki+L=LDizBJmFUieMDg9J=U6mn6XxTPPkAaWiyppTouTzaqw@mail.gmail.com>
Date:   Mon, 17 May 2021 21:47:12 +0200
Message-ID: <87y2cddtxb.ffs@nanos.tec.linutronix.de>
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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.

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

Thanks,

        tglx