Re: [PATCH v6 21/21] s390: doc: detailed specifications for AP virtualization

[Harald Freudenberger]

On 02.07.2018 18:28, Halil Pasic wrote:
>
>
> On 06/29/2018 11:11 PM, Tony Krowiak wrote:
>> This patch provides documentation describing the AP architecture and
>> design concepts behind the virtualization of AP devices. It also
>> includes an example of how to configure AP devices for exclusive
>> use of KVM guests.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
>> ---
> [..]
>> +
>> +Reserve APQNs for exclusive use of KVM guests
>> +---------------------------------------------
>> +The following block diagram illustrates the mechanism by which APQNs are
>> +reserved:
>> +
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +------------------+
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ removeÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂ unbind
>> +ÂÂÂÂÂÂÂÂ +------------------->+ cex4queue driver +<-----------+
>> +ÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +------------------+ÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |
>> ++--------+---------+ register +------------------+ÂÂÂÂÂ +-----+------+
>> +|ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +<---------+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ | bind |ÂÂÂÂÂÂÂÂÂÂÂ |
>> +| ap_bus | | vfio_ap driver +<-----+ admin |
>> +|ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +--------->+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂ |
>> ++------------------+Â probeÂÂ +---+--------+-----+ÂÂÂÂÂ +------------+
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ create |ÂÂÂÂÂÂÂ | store APQN
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vÂÂÂÂÂÂÂ v
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +---+--------+-----+
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â matrix deviceÂÂ |
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +------------------+
>> +
>> +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:
>> +Â * Create the 'vfio_ap' root device - /sys/devices/vfio_ap
>> +Â * Create the 'matrix' device in the 'vfio_ap' root
>> +Â * Register the matrix device with the device core
>> +* Register with the ap_bus for AP queue devices of type 10 devices (CEX4 and
>> +Â newer) and to provide the vfio_ap driver's probe and remove callback
>> +Â interfaces. The reason why older devices are not supported is because there
>> +Â are no systems available on which to test.
>> +* The admin unbinds queue cc.qqqq from the cex4queue device driver. This results
>> +Â in the ap_bus calling the the device driver's remove interface which
>> +Â unbinds the cc.qqqq queue device from the driver.
>
> What if the queue cc.qqqq is already in use? AFAIU unbind is almost as radical as
> pulling a cable. What is the proper procedure an admin should follow before doing
> the unbind?
What do you mean on this level with 'in use'? A unbind destroys the association
between device and driver. There is no awareness of 'in use' or 'not in use' on this
level. This is a hard unbind.
>
>> +* The admin binds the cc.qqqq queue to the vfio_ap device driver. This results
>> +Â in the ap_bus calling the device vfio_ap driver's probe interface to bind
>> +Â queue cc.qqqq to the driver. The vfio_ap device driver will store the APQN for
>> +Â the queue in the matrix device
>> +
> [..]
>
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