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

Peter Krempa pkrempa at redhat.com
Fri Nov 6 06:42:35 UTC 2015

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:

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.

By being a bit more aggresive we could also cut off the need to use
QEMU_CAPS_DEVICE (as you've pointed out further down) and possibly even
mandate the use of QMP which was initially added by qemu 0.12.0 but I
remember that there were some problems with that.

I'm realizing though that picking the line where we cut support is
really hard, but I think it will pay off eventually. Even with the
proposed state.

> By dropping support for anything older than QEMU 0.12.0
> we can remove the code for parsing stderr. The QEMU 0.12.0

I'm so happy to see all that code go away.

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