linux-kernel - Re: [PATCH 11/14] irq: add support for allocating (and affinitizing) sets of IRQs

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Date:   Tue, 30 Oct 2018 18:46:06 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jens Axboe <axboe@...nel.dk>
cc:     Keith Busch <keith.busch@...el.com>, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/14] irq: add support for allocating (and affinitizing)
 sets of IRQs

On Tue, 30 Oct 2018, Jens Axboe wrote:
> On 10/30/18 11:25 AM, Thomas Gleixner wrote:
> > Jens,
> > 
> > On Tue, 30 Oct 2018, Jens Axboe wrote:
> >> On 10/30/18 10:02 AM, Keith Busch wrote:
> >>> pci_alloc_irq_vectors_affinity() starts at the provided max_vecs. If
> >>> that doesn't work, it will iterate down to min_vecs without returning to
> >>> the caller. The caller doesn't have a chance to adjust its sets between
> >>> iterations when you provide a range.
> >>>
> >>> The 'masks' overrun problem happens if the caller provides min_vecs
> >>> as a smaller value than the sum of the set (plus any reserved).
> >>>
> >>> If it's up to the caller to ensure that doesn't happen, then min and
> >>> max must both be the same value, and that value must also be the same as
> >>> the set sum + reserved vectors. The range just becomes redundant since
> >>> it is already bounded by the set.
> >>>
> >>> Using the nvme example, it would need something like this to prevent the
> >>> 'masks' overrun:
> >>
> >> OK, now I hear what you are saying. And you are right, the callers needs
> >> to provide minvec == maxvec for sets, and then have a loop around that
> >> to adjust as needed.
> > 
> > But then we should enforce it in the core code, right?
> 
> Yes, I was going to ask you if you want a followup patch for that, or
> an updated version of the original?

Updated combo patch would be nice :)

Thanks

	lazytglx