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

[Pierre Morel]

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:
> > > +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 CEX4, CEX5 and
> > > +Â 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 BÃblingen - Germany