[rdo-dev] qemu-kvm vs qemu-kvm-rhev requirement

Haïkel Guémar hguemar at redhat.com
Tue Jun 5 13:45:42 UTC 2018

On 06/05/2018 11:28 AM, Roman Kagan wrote:
> On Tue, Jun 05, 2018 at 10:26:54AM +0200, Kashyap Chamarthy wrote:
>> On Mon, Jun 04, 2018 at 09:41:07PM +0300, Roman Kagan wrote:
>>> Not so long ago openstack-nova started to require qemu-kvm-rhev instead
>>> of qemu-kvm.
>>> This made it impossible to install on Virtuozzo, which used to work well
>>> before the change.
>> I think Virtuozzo is based on CentOS.
> Right, to a large extent.  However, our QEMU package is much closer to
> qemu-kvm-rhev than to CentOS' qemu-kvm.  It's still different from
> qemu-kvm-rhev in some respects so we don't feel comfortable providing
> "qemu-kvm-rhev" in our package.

The thing is EL7 is stuck at RPM 4.11.x. If we had RPM 4.13.x, we could 
have used boolean dependencies to do that:

Requires: qemu-kvm-rhev >= 2.9.0 or qemu-kvm-virtuozzo >= x.y.z

Meanwhile, we don't have much alternatives than the one already 
suggested to provide qemu-kvm-rhev

>>> I skimmed through the related tickets
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1367696
>>> https://review.rdoproject.org/r/1900
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1392820
>>> https://review.rdoproject.org/r/9858
>>> but failed to understand the motivation behind this change.  What are
>>> those particular features that are only present in qemu-kvm-rhev and
>>> make the vendor-neutral requirement insufficient?  So far we didn't
>>> notice any issues running recent enough QEMU with Nova, but I guess this
>>> must have changed.
>> Dan has already responded.  In short, 'qemu-kvm-rhev' is the recommended
>> RPM for Red Hat OSP.
> This is clear :)  I'm interested in a longer reply to "why", in order to
> figure out how to correctly run Nova on top of Virtuozzo.
> Thanks,
> Roman.

In short, it's a trimmed version of qemu-kvm for enterprise users:
* unsupported devices/features are disabled
* features backported from the next branch (including support for newer CPU)
Most patches are linked to an upstream pull request, or a ticket for bugs.

In our case, I think we're mostly interested in live migration features 
backports, but that might not be accurate or up-to-date as I'm not 
focusing on compute.


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