Re: [Qemu-devel] [PATCH/RFC 2/3] s390x/ais: enable ais when migration is available

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 25 Sep 2017 12:12:49 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 09/25/2017 12:07 PM, Cornelia Huck wrote:
> > On Fri, 22 Sep 2017 16:27:00 +0200
> > Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
> >   
> >> One thing I would find very helpful is what do we expect to work and not
> >> work for which version. Kind of a matrix. For instance should vfio pci
> >> work for versions prior 2.11. I think in the not so distant past we
> >> changed how SIC works (so it complains when we don't have ais).  
> > 
> > A matrix sounds like a good idea.  
> 
> I think we do not even need a matrix, a minimum level will suffice because...
> > 
> > I don't think we really ever had a setup that worked out of the box  
> 
> exactly: ...it never worked until 2.10 and we do not have libvirt support yet.
> Now with the fix 2.10 will also not work, so I think its fair to say
> 
> PCI passthrough via VFIO will be supported for 
> - KVM: host kernel >= 4.13
> - TCG: TBD
> - QEMU >= 2.11
> - libvirt TBD

Make that zpci-per-se, no?

with KVM: host kernel >= 4.13 && QEMU >= 2.11
with TCG: tbd, I don't think anybody has time to wire this up for 2.11

Apropos libvirt: How will it determine whether zpci should be
supported? There are some old QEMU + KVM combinations out there that
will have a phb (but not be usable by stock Linux guests as the feature
bits are missing). Version fence? Check for cpu feature support?