[libvirt] [PATCH 0/7] Drop support for QEMU < 0.12.0

[Daniel P. Berrange]

On Fri, Nov 06, 2015 at 07:42:35AM +0100, Peter Krempa wrote:
> On Thu, Nov 05, 2015 at 17:33:52 +0000, Daniel Berrange wrote:
> > The patches for introducing virtlogd will be significantly
> > simplified if we don't need to worry about parsing stderr
> > during startup. This is required prior to QEMU 0.11 so
> > that we can get the dyanamically allocated /dev/pty/NNN
> > paths.
> 
> I'm so glad to see something like this. Not only to simplify adding
> virtlogd but also we will be able to remove some _very_ old cruft.
> 
> > The QEMU 0.12.1 release was shipped in RHEL-6 vintage
> > distros and is already quite old, so seems like a fair
> > target version to aim for as the minimum required.
> 
> I'd like to add that I think this is still too vintage. It's now almost
> 6 years from that point:
> 
> commit 6c412ddf1cc0c41a7c36064a4a9c428e99c52ff8
> Author: Anthony Liguori <aliguori at us.ibm.com>
> Date:   Sat Dec 19 08:23:00 2009 -0600
> 
>     Update for 0.12.0 release
> 
> and right after that:
> 
> 
> commit fe1b69708c72b163d3acdf2bb012e169d2d3dda0
> Author: Anthony Liguori <aliguori at us.ibm.com>
> Date:   Sat Dec 19 19:31:18 2009 -0600
> 
>     Update version and changelog for 0.12.1
> 
> The initial qemu version in RHEL-6 was indeed 0.12.1, but if you look at
> the current state of it you'll notice that it was patched quite a lot so
> it rather stopped to resemble the 0.12 release and was really holding up
> with upstream for quite a while. Libvirt was even rebased during the
> current lifetime of rhel/centos 6 distros to 0.10.2 (and it has quite a
> few patches on top of that too). Libvirt 0.10.2 was released almost 3
> years after qemu 0.12.0:

Although QEMU 0.12.1 in RHEL6 is heavily patched with feature backports,
when picking a target min version, I'm really lookng at the approximate
"vintage" rather than the specific featureset of RHEL6 QEMU. As another
benchmark of the same vintage, Debian Squeeze has QEMU 0.12.5. I just
round off the micro version, so pick 0.12.0.

> commit f8fbeb50d52520a109d71c8566fed2ea600650ec
> Author: Daniel Veillard <veillard at redhat.com>
> Date:   Mon Sep 24 12:06:05 2012 +0800
> 
>     Release of libvirt-0.10.2
> 
> So while having rhel-6 as a support target might look cool, nobody would
> actually use such old code anyways, since they can get tested and
> patched packages with a ton of new features.

I am rather conservative about pushing min versions, since IME many
corporates tend to stick with ancient versions of software for much
longer than people tend to realize. At this time RHEL-6 is almost
certainly the largest deployment / user base for libvirt / QEMU out
of all the RHEL versions. It will be a while before RHEL-7 overtakes
it to become the dominant RHEL platform. As such I think it is important
that libvirt upstream continue to be buildable against RHEL-6 and target
the QEMU 0.12.x series that includes (even though RHEL6 QEMU is rather
a frakenmonster of backports at this time)

Regards,
Daniel
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