linux-kernel - Re: [PATCH 1/2] genirq/affinity: remove rsvd check against minvec

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Date: Fri, 10 May 2024 10:47:50 -0600
From: Keith Busch <kbusch@...nel.org>
To: Ming Lei <ming.lei@...hat.com>
Cc: Keith Busch <kbusch@...a.com>, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org, hch@....de, tglx@...utronix.de
Subject: Re: [PATCH 1/2] genirq/affinity: remove rsvd check against minvec

On Fri, May 10, 2024 at 11:15:54PM +0800, Ming Lei wrote:
> On Fri, May 10, 2024 at 07:14:58AM -0700, Keith Busch wrote:
> > From: Keith Busch <kbusch@...nel.org>
> > 
> > The reserved vectors are just the desired vectors that don't need to be
> > managed.
> > 
> > Signed-off-by: Keith Busch <kbusch@...nel.org>
> > ---
> >  kernel/irq/affinity.c | 3 ---
> >  1 file changed, 3 deletions(-)
> > 
> > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
> > index 44a4eba80315c..74b7cccb51a16 100644
> > --- a/kernel/irq/affinity.c
> > +++ b/kernel/irq/affinity.c
> > @@ -113,9 +113,6 @@ unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
> >  	unsigned int resv = affd->pre_vectors + affd->post_vectors;
> >  	unsigned int set_vecs;
> >  
> > -	if (resv > minvec)
> > -		return 0;
> > -
> 
> This behavior is introduced in 6f9a22bc5775 ("PCI/MSI: Ignore affinity if pre/post
> vector count is more than min_vecs"), which is one bug fix.

Thanks for the pointer. Probably best I avoid messing with irq code just
for this use case, so I can have the driver disable the PCI_IRQ_AFFINTY
flag instead ... assuming hch doesn't "nak" it.  :)