linux-kernel - Re: [RFC PATCH 1/4] genirq: Provide basic NMI management for interrupt lines

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Message-ID: <alpine.DEB.2.21.1807172144570.1817@nanos.tec.linutronix.de>
Date:   Tue, 17 Jul 2018 21:46:29 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Julien Thierry <julien.thierry@....com>
cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        ricardo.neri-calderon@...ux.intel.com, marc.zyngier@....com,
        mingo@...nel.org
Subject: Re: [RFC PATCH 1/4] genirq: Provide basic NMI management for interrupt
 lines

On Tue, 17 Jul 2018, Julien Thierry wrote:
> On 17/07/18 16:51, Peter Zijlstra wrote:
> > On Tue, Jul 17, 2018 at 04:48:17PM +0100, Julien Thierry wrote:
> > > Supporting desc->affinity_hint for NMIs shouldn't be an issue, right?
> > 
> > Shouldn't NMIs be strictly per cpu interrupt sources?
> 
> That's a good question, and I don't have a proper answer right now...
> 
> However, per cpu or not, the affinity still needs to be set for that
> interrupt. It seemed to me that the desc->affinity_hint was just a way to keep
> track of the interrupt affinity when it gets set through
> irq_set_affinity_hint.
> 
> Is that not the case?

No the affinity hint is a way to tell user space irqbalanced what the
driver thinks is the best placement. Affinity settings are done by the
kernel internal interfaces and those do not care about the hint at all.

Thanks,

	tglx