Subject: Re: [PATCH v5 3/6] iommu/arm-smmu-v3: Suppress EVTQ/PRIQ events in kdump kernel

From: Jason Gunthorpe <[email-masked]>
Date: Tue, 19 May 2026 19:27:49 -0300

On Tue, May 19, 2026 at 01:13:09PM -0700, Nicolin Chen wrote:
> On Tue, May 19, 2026 at 02:44:53PM -0300, Jason Gunthorpe wrote:
> > On Sun, May 10, 2026 at 02:23:02PM -0700, Nicolin Chen wrote:
> > > @@ -2364,6 +2364,14 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
> > >  	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
> > >  				      DEFAULT_RATELIMIT_BURST);
> > >  
> > > +	/*
> > > +	 * A combined IRQ might call into this function with the queue disabled.
> > > +	 * E.g. kdump, where stale HW PROD vs SW CONS would drive a bogus drain
> > > +	 * and a CONS write to a disabled queue.
> > > +	 */
> > > +	if (!(readl_relaxed(smmu->base + ARM_SMMU_CR0) & CR0_EVTQEN))
> > > +		return IRQ_NONE;
> > 
> > I don't think we should be doing register reads on these paths. 
> > 
> > Why not load a different irq function instead?
> 
> Yea. Perhaps we could even entirely skip their IRQ requests. Only
> gerror should be kept in kdump case.

Yeah, if the irq handlers don't do anything then don't register them
makes alot of sense..

Jason