Re: [PATCH v4 15/15] s390: doc: detailed specifications for AP virtualization

Pierre Morel
2018-04-17T16:25:50Z

On 17/04/2018 18:14, Tony Krowiak wrote:
> On 04/16/2018 09:13 AM, Pierre Morel wrote:
>> On 15/04/2018 23:22, Tony Krowiak wrote:
>>> This patch provides documentation describing the AP architecture and
>>> design concepts behind the virtualization of AP devices. It also
>>>
...snip...
>>> +The process for reserving an AP queue for use by a KVM guest is:
>>> +
>>> +* The vfio-ap driver during its initialization will perform the
>>> following:
>>> +  * Create the 'vfio_ap' root device - /sys/devices/vfio_ap
>>> +  * Create the 'matrix' device in the 'vfio_ap' root
>>> +  * Register the matrix device with the device core
>>> +* Register with the ap_bus for AP queue devices of type CEX4, CEX5 and
>>> +  CEX6 and to provide the vfio_ap driver's probe and remove
>>> callback interfaces.
>>
>> I wonder why the type of card has anything to do with this driver.
>> It should be transparent, the driver should be able to provide the
>> matrix (APM/AQM/ADM)
>> independently from the type of card in the slot.
>
> We've been down this road several times before. We are only supporting
> virtualization of
> CEX4 and newer cards. Also, the AP bus requires registering for
> specific card types.

Yes I know, but the AP BUS design may be not the optimal for the AP Matrix.
The AP Matrix is device independent.
We just write/clear bits in a matrix and we do not care what is plugged.

So may be make clear that this device dependence is due to the actual AP
BUS interface design.

>
>>
>>
>> Regards,
>>
>> Pierre
>>
>

--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany