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

[Tony Krowiak]

On 04/17/2018 12:25 PM, Pierre Morel wrote:
> 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.

Okay, will do.

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