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Re: [libvirt] cpuset / numa and qemu in TCG mode



On Mon, May 11, 2015 at 01:14:58PM +0200, Martin Kletzander wrote:

> Determining this by version might not be reliable, but more
> importantly working around bug in underlying software is something
> that shouldn't be done at all IMHO.  Let the maintainers backport
> whatever needs to be done.

I agree with you in an ideal world but there are times when we do need
to add work arounds in $project_x to work around issues in $project_y.
 
> >Ther nova side will be pretty easy regardless.
> >
> >I'd say the best solution would be to back port the 'fix' but that seems like a
> >lot of effort given the number of distros and libvirt versions potentiall
> >involved.
> >
> 
> If you want the fix to be distro-agnostic, there's nothing easier than
> back-porting the fix into our upstream maintenance branches.  Those
> should make the life of distro maintainers easy (although it looks
> like not many distros use it).

And this is part of the problem.  If I understand correctly Ubuntu cloud-archive
is using libvirt 1.2.12 which is *NOT* a maintenance release so that leaves us
with doing an additional backport to 1.2.12 and getting the cloud-archive team
to take it[1]  or Adding a hack to nova.  And that's just Ubuntu It's hard to
say for sure that some vendor isn't running libvirt 1.2.12 also.
 
> Having said that I'm not sure which commit(s) are those that need to
> be back-ported.  Having known your libvirt version, it shouldn't be
> too hard looking for the differences and finding the right commit.
> When back-porting request is made on the list, it is usually acted
> upon.  If you can't find the exact commit, let me know and I'll do my
> best to help.

So a git bisect points at:
---
commit a103bb105c0c189c3973311ff1826972b5bc6ad6
Author: Daniel P. Berrange <berrange redhat com>
Date:   Tue Feb 10 15:59:57 2015 +0000

    qemu: fix setting of VM CPU affinity with TCG
---

A small amount of reading implies to me that we'd be looking at backporting
a103bb105c0c189c3973311ff1826972b5bc6ad6 to any maintenance branch that contains
b07f3d821dfb11a118ee75ea275fd6ab737d9500.  Which I think is 1.2.13 only, but I
could be wrong.

If you don't beat me to it I'll request that backport to 1.2.13 *and* ask the
Ubuntu guys to take it as well.

I have to admit I'm still in 2 minds on the nova side.  Adding a wart to the
libvirt driver for this specific bug for distros/vendors that are using 1.2.12
seems a bit gross but ....

Daniel what do you think?

Yours Tony.

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