linux-kernel - Re: [PATCH 1/6] genirq: platform wide interrupt moderation: Documentation, Kconfig, irq

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Message-ID: <86h5uxu56z.wl-maz@kernel.org>
Date: Thu, 13 Nov 2025 19:02:12 +0000
From: Marc Zyngier <maz@...nel.org>
To: Luigi Rizzo <lrizzo@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Luigi Rizzo <rizzo.unipi@...il.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH 1/6] genirq: platform wide interrupt moderation: Documentation, Kconfig, irq_desc

On Thu, 13 Nov 2025 14:55:55 +0000,
Luigi Rizzo <lrizzo@...gle.com> wrote:
> 
> On Thu, Nov 13, 2025 at 3:42 PM Marc Zyngier <maz@...nel.org> wrote:
> > [...]
> 
> >
> > The descriptions are also massively x86-specific. That's probably OK
> > for the stuff you care about, but I'd certainly would want things to
> > be a bit more abstract and applicable to all architectures.
> 
> Absolutely.
> 
> > I also note that since you explicitly check for handle_edge_irq() in
> > set_moderation_mode(), this will not work on anything GIC related, or
> > any other architecture that uses the fasteoi flows. I really wonder
> > why you are not looking at the actual trigger mode instead...
> 
> sure, that would be the best thing. Any suggestions on how to fix the
> check ?

I made that suggestion already: check the trigger mode (the interrupt
"type") and only apply this to edge interrupts (and stop mentioning
MSIs, for which some architectures have a level variant).

> > Until you fix it, please refrain from touching the GICv3 code, and
> > make sure this is solely enabled on x86 -- it clearly wasn't tested on
> > anything else.
> 
> FWIW I did verify correct operation and performance boost on arm64,
> both network and nvme (this was a previous version which
> did not restrict to handle_edge_irq).

You do realise that what is not on the list doesn't exist, right? ;-)

> Also FWIW there should be nothing architecture-specific in this series.

We're in strong agreement here.

	M.

-- 
Without deviation from the norm, progress is not possible.