Re: [qemu-s390x] [RFC 00/19] KVM: s390/crypto/vfio: guest dedicated crypto adapters

[Pierre Morel]

On 16/11/2017 16:23, Tony Krowiak wrote:
> On 11/14/2017 08:57 AM, Cornelia Huck wrote:
> > On Tue, 31 Oct 2017 15:39:09 -0400
> > Tony Krowiak <address@hidden> wrote:
> >
> > > On 10/13/2017 01:38 PM, Tony Krowiak wrote:
> > > Ping
> > > > Tony Krowiak (19):
> > > >     KVM: s390: SIE considerations for AP Queue virtualization
> > > >     KVM: s390: refactor crypto initialization
> > > >     s390/zcrypt: new AP matrix bus
> > > >     s390/zcrypt: create an AP matrix device on the AP matrix bus
> > > >     s390/zcrypt: base implementation of AP matrix device driver
> > > >     s390/zcrypt: register matrix device with VFIO mediated device
> > > >       framework
> > > >     KVM: s390: introduce AP matrix configuration interface
> > > >     s390/zcrypt: support for assigning adapters to matrix mdev
> > > >     s390/zcrypt: validate adapter assignment
> > > >     s390/zcrypt: sysfs interfaces supporting AP domain assignment
> > > >     s390/zcrypt: validate domain assignment
> > > >     s390/zcrypt: sysfs support for control domain assignment
> > > >     s390/zcrypt: validate control domain assignment
> > > >     KVM: s390: Connect the AP mediated matrix device to KVM
> > > >     s390/zcrypt: introduce ioctl access to VFIO AP Matrix driver
> > > >     KVM: s390: interface to configure KVM guest's AP matrix
> > > >     KVM: s390: validate input to AP matrix config interface
> > > >     KVM: s390: New ioctl to configure KVM guest's AP matrix
> > > >     s390/facilities: enable AP facilities needed by guest
> > I think the approach is fine, and the code also looks fine for the most
> > part. Some comments:
> >
> > - various patches can be squashed together to give a better
> >    understanding at a glance
> Which patches would you squash?
> > - this needs documentation (as I already said)
> My plan is to take the cover letter patch and incorporate that into 
> documentation,
> then replace the cover letter patch with a more concise summary.
> > - some of the driver/device modelling feels a bit awkward (commented in
> >    patches) -- I'm not sure that my proposal is better, but I think we
> >    should make sure the interdependencies are modeled correctly
> I am responding to each patch review individually.

I think that instead of responding to each patch individually we should 
have a discussion on the design because I think a lot could change and 
discussing about each patch as they may be completely redesigned for the 
next version may not be very useful.

So I totally agree with Conny on that we should stabilize the 
bus/device/driver modeling.

I think it would be here a good place to start the discussion on things 
like we started to discuss, Harald and I, off-line:
- why a matrix bus, in which case we can avoid it
- which kind of devices we need
- how to handle the repartition of queues on boot, reset and hotplug
- interaction with the host drivers
- validation of the matrix for guests and host views

or even features we need to add like
- interruptions
- PAPQ/TAPQ-t and APQI interception
- virtualization of the AP
- CPU model and KVM capabilities

In my understanding these points must be cleared before we really start 
to discuss the details of the implementation.

Best regards,

Pierre

> > - some minor stuff


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