linux-kernel - Re: [PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the vfio

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Date:   Mon, 18 Feb 2019 11:35:45 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     pmorel@...ux.ibm.com, borntraeger@...ibm.com,
        alex.williamson@...hat.com, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        frankja@...ux.ibm.com, pasic@...ux.ibm.com, david@...hat.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the
 vfio_ap bus subsystem

On 2/18/19 7:01 AM, Cornelia Huck wrote:
> On Fri, 15 Feb 2019 16:59:33 -0500
> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
> 
>> On 2/15/19 4:11 AM, Cornelia Huck wrote:
>>> On Thu, 14 Feb 2019 13:30:59 -0500
>>> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>>>    
>>>> On 2/14/19 12:36 PM, Pierre Morel wrote:
>>>>> On 14/02/2019 17:57, Cornelia Huck wrote:
> 
>>>>>> (And reading further in the current code, it seems we clear that
>>>>>> structure _after_ the matrix device had been setup, so how can that
>>>>>> even work? Where am I confused?)
>>>>>
>>>>> On device_register there were no bus, so the core just do not look for a
>>>>> driver and this field was nor tested nor overwritten.
>>>
>>> Hm... so has the callback in driver_for_each_device() in
>>> vfio_ap_verify_queue_reserved() ever been invoked at all? It seems this
>>> patch fixes more than just libudev issues...
>>
>> It is this patch that rendered the driver_for_each_device() in
>> vfio_ap_verify_queue_reserved() erroneous. That function gets called
>> every time an adapter or domain is assigned to the mdev. This patch
>> introduced the problem with driver_for_each_device().
> 
> So, does this function need to be removed or called from another place,
> then? (It looks like it was dead code before.)

I don't see why you think it's dead code:

assign_adapter_store
==> vfio_ap_mdev_verify_queues_reserved_for_apid
     ==> vfio_ap_verify_queue_reserved
         ==> driver_for_each_device

The only way that the vfio_ap_verify_queue_reserved - the function that
calls driver_for_each_device - does not get called is if no bits have
yet been set in matrix_mdev->matrix.aqm.

>