linux-kernel - Re: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the vfio

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Message-Id: <d2eb352c-274b-5c1d-0c3c-33e13eff2c88@de.ibm.com>
Date:   Thu, 21 Feb 2019 13:35:02 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     pmorel@...ux.ibm.com, Halil Pasic <pasic@...ux.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     Tony Krowiak <akrowiak@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        frankja@...ux.ibm.com, david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com
Subject: Re: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the
 vfio_ap bus subsystem



On 21.02.2019 13:10, Pierre Morel wrote:
> On 20/02/2019 13:51, Halil Pasic wrote:
>> On Wed, 20 Feb 2019 10:27:31 +0100
>> Cornelia Huck <cohuck@...hat.com> wrote:
>>
>>> On Tue, 19 Feb 2019 22:31:17 +0100
>>> Pierre Morel <pmorel@...ux.ibm.com> wrote:
>>>
>>>> On 19/02/2019 19:52, Tony Krowiak wrote:
>>>>> On 2/18/19 1:08 PM, Pierre Morel wrote:
>>>>>> Libudev relies on having a subsystem link for non-root devices. To
> 
> ...snip...
> 
>>>>>> +
>>>>>> +static struct device_driver matrix_driver = {
>>>>>> +    .name = "vfio_ap",
>>>>>
>>>>> This is the same name used for the original device driver. I think
>>>>> this driver ought to have a different name to avoid confusion.
>>>>> How about vfio_ap_matrix or some other name to differentiate the
>>>>> two.
>>>>
>>>> I would like too, but changing this will change the path to the mediated
>>>> device supported type.
>>>
>>> Yes, we don't want to change that.
>>>
>>
>> Nod.
> 
> However if I cannot change the driver name, I can change the bus name to matrix.
> At least one less "vfio_ap" name
> 
>>
>>>>
>>>>
>>>>>   
>>>>>> +    .bus = &matrix_bus,
>>>>>> +    .probe = matrix_probe,
>>>>>
>>>>> I would add:
>>>>>       .suppress_bind_attrs = true;
>>>>>
>>>>> This will remove the sysfs bind/unbind interfaces. Since there is only
>>>>> one matrix device and it's lifecycle is controlled herein, there is no
>>>>> sense in allowing a root user to bind/unbind it.
>>>>>    
>>>>
>>>> OTOH bind/unbind has no impact.
>>>> If no one else ask for this I will not change what has already been
>>>> reviewed by Conny and Christian.
>>>
>>> As we only have one driver, it does not really make sense anyway.
>>>
>>
>> I see this as a reason to suppress_bind_attrs. It is much easier than to
>> think about what should happen when one unbinds the matrix device from
>> the vfio_ap driver on the vfio_ap bus. With the code as is it seems to
>> just keep working as if nothing happened.
>> And /sys/devices/vfio_ap/matrix/mdev_supported_types/ referencing the
>> name of the driver that is already gone sounds a bit weird.
>>
>> Regards,
>> Halil
>>
> 
> If there is no objection I will do this,
> It seems more logical to me too.

Go ahead and send this as v3?