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 11:47:39 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Thomas Gleixner <tglx@...utronix.de>
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 10/30/18 11:46 AM, Thomas Gleixner wrote:
> 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 :)

I'll re-post the series with the updated combo some time later today.

> 	lazytglx

I understand :-)

-- 
Jens Axboe