linux-kernel - Re: [PATCH 0/2] s390/vfio-ap: do not open code locks for VFIO_GROUP_NOTIFY_SET

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Date:   Fri, 20 Aug 2021 10:24:20 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Cc:     Halil Pasic <pasic@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, pasic@...ux.vnet.ibm.com,
        jjherne@...ux.ibm.com, jgg@...dia.com, kwankhede@...dia.com,
        david@...hat.com, pbonzini@...hat.com, frankja@...ux.ibm.com,
        imbrenda@...ux.ibm.com
Subject: Re: [PATCH 0/2] s390/vfio-ap: do not open code locks for
 VFIO_GROUP_NOTIFY_SET_KVM notification



On 8/19/21 11:30 AM, Cornelia Huck wrote:
> On Wed, Aug 18 2021, Alex Williamson <alex.williamson@...hat.com> wrote:
>
>> On Wed, 18 Aug 2021 17:59:51 +0200
>> Christian Borntraeger <borntraeger@...ibm.com> wrote:
>>
>>> On 02.08.21 18:32, Tony Krowiak wrote:
>>>>
>>>> On 8/2/21 9:53 AM, Halil Pasic wrote:
>>>>> On Mon, 2 Aug 2021 09:10:26 -0400
>>>>> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>>>>>   
>>>>>> PING!
>>>>>>
>>>>>> This patch will pre-req version 17 of a patch series I have waiting in
>>>>>> the wings,
>>>>>> so I'd like to get this one merged ASAP. In particular, if a KVM
>>>>>> maintainer can
>>>>>> take a look at the comments concerning the taking of the kvm->lock
>>>>>> before the
>>>>>> matrix_mdev->lock it would be greatly appreciated. Those comments begin with
>>>>>> Message ID <20210727004329.3bcc7d4f.pasic@...ux.ibm.com> from Halil Pasic.
>>>>> As far as I'm concerned, we can move forward with this. Was this
>>>>> supposed to go in via Alex's tree?
>>>> I am not certain, Christian queued the previous patches related to
>>>> this on:
>>>>
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/log/?h=fixes
>>>>
>>>> Jason G., since this will need to be integrated with your other patches,
>>>> where should this be queued?
>>>
>>> This previous patch (s390/vfio-ap: clean up mdev resources when remove callback invoked) is
>>> already in master.
>>> Can you respin the series with all Acks and RBs?
>>>
>>> Alex, can you then take these 2 patches via your tree? Thanks
>>>
>>> Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
>>> for this series.
>>
>> I see some review feedback that seems to suggest a new version would be
>> posted:
>>
>> https://lore.kernel.org/linux-s390/0f03ab0b-2dfd-e1c1-fe43-be2a59030a71@linux.ibm.com/
> Yeah, I thought so as well. But it also looks like something that could
> be a fixup on top.

I will post the new patch today. I was waiting for the remainder of
the feedback and frankly forgot to post the patch incorporating
the changes precipitated by the previous comments.

>
>> I also see in this thread:
>>
>> https://lore.kernel.org/linux-s390/20210721164550.5402fe1c.pasic@linux.ibm.com/
>>
>> that Halil's concern's around open/close races are addressed by Jason's
>> device_open/close series that's already in my next branch and he
>> provided an Ack, but there's still the above question regarding the
>> kvm->lock that was looking for a review from... I'm not sure, maybe
>> Connie or Paolo.  Christian, is this specifically what you're ack'ing?
> I'm also unsure about the kvm->lock thing. Is taking the lock buried
> somewhere deep in the code that will ultimately trigger the release?
> I would at least like a pointer.

I'm not quite sure what you're asking here, but if you follow the
thread starting with the link above it may reveal the answer to
what you are asking here.


>
>> It can ultimately go in through my tree, but not being familiar with
>> this code I'd hope for more closure.  Thanks,
>>
>> Alex