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

[Pierre Morel]

On 16/11/2017 18:03, Cornelia Huck wrote:
> On Thu, 16 Nov 2017 17:06:58 +0100
> Pierre Morel <address@hidden> wrote:
>
> > 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
>
> I thought it had been agreed that we should be able to ditch it?

I have not see any comment on the matrix bus.

> > - which kind of devices we need
>
> What is still unclear? Which card generations to support?

No, I mean the relation bus/device/driver/mdev...

> > - how to handle the repartition of queues on boot, reset and hotplug
>
> That's something I'd like to see a writeup for.

yes, and it may have an influence on the bus/device/driver/mdev design

> > - interaction with the host drivers
>
> The driver model should already handle that, no?

yes it should, but it is not clear for me.

> > - validation of the matrix for guests and host views
>
> I saw validation code in the patches, although I have not reviewed it.
>
> > or even features we need to add like
> > - interruptions
>
> My understanding is that interrupts are optional so they can be left
> out in the first shot. With the gisa (that has not yet been posted), it
> should not be too difficult, no?

you are right I forgot that it is optional

> > - PAPQ/TAPQ-t and APQI interception
>
> I can't say anything about that, as this is not documented :(

Right we can live without these too.

> > - virtualization of the AP
>
> Is this really needed? It would complicate everything a lot.

Concern has no sens without interception.
> > - CPU model and KVM capabilities
>
> That already has been discussed with the individual patches.

Well, if there are no interceptions the individual patches discussions 
are enough.

> > In my understanding these points must be cleared before we really start
> > to discuss the details of the implementation.
>
> The general design already looks fine to me. Do you really expect that
> a major redesign is needed?

I am worry about the following:
- Will the matrix bus be accepted
- What happens on host reset and hot plug/unplug in host
- What happens with the queues on guest start/halt/restart

Regards,

Pierre

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