Re: [Xen-devel] [libvirt] Fixing libvirt's libxl driver breakage -- where to define LIBXL_API_VERSION?

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

(Adding Jan Beulich)

Ian Jackson writes ("Re: [libvirt] [Xen-devel] Fixing libvirt's libxl driver 
breakage -- where to define LIBXL_API_VERSION?"):
> It seems that the libvirt LIBXL_API_VERSION is now rather higher, at
> 0x040400, since libvirt#fccf27253ced
>   libxl: switch to using libxl_domain_create_restore from v4.4 API
> 
> One unfortunate effect of this is to break the osstest tests of the
> Xen 4.3 stable branch, which for the moment is still allegedly in
> security support.
> 
> I can't really see a way that this kind of problem could be avoided
> in principle, without
>   - providing a more sophisticated way for libxl callers to set the
>     requested version
>   - providing more compatibility code in libvirt, too, and retaining
>     it for some time
> 
> I think instead that it would probably be better for osstest to
> "freeze" the version of libvirt that it is using, every time we branch
> Xen.
> 
> So Xen 4.4 would be tested with whatever libvirt we were using when
> the stable branch for Xen 4.4 was made, and so on.
> 
> Does that sound sensible ?

In the assumption that it is, I have:

Created the following branch refs on xenbits in the toplevel
libvirt.git:

 osstest/frozen/xen-4.3-testing 9a0c7f5f834185db9017c34aabc03ad99cf37bed
 osstest/frozen/xen-4.4-testing 33fb8ff185846a7b4974105d2c9400690a6f95cf
 osstest/frozen/xen-4.5-testing cda1cc170f07b45911b3dad03e42c8ebfc210fa1
 osstest/frozen/xen-4.6-testing eac167e2610d3e59b32f7ec7ba78cbc8c420a425
 osstest/frozen/xen-4.7-testing 1a41ed5af5e1704dd9b0bdca40df5c9cacbdabfc

These were those tested by the following `tolerable' osstest push gate
flights for the corresponding Xen tree:

 xen-4.3-testing 9a0c7f5f8341 86673
 xen-4.4-testing 33fb8ff18584 85031
 xen-4.5-testing cda1cc170f07 83135
 xen-4.6-testing eac167e2610d 96031
 xen-4.7-testing 1a41ed5af5e1 95728

And I have prepared the patch below, which (together with a
prerequisite, in my tree) will implement this in osstest.

Ian.

From 5d1c91d3c53b580305e96d62f8ca84f85f8d3011 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Date: Mon, 27 Jun 2016 16:49:52 +0100
Subject: [OSSTEST PATCH] cr-daily-branch: libvirt: use frozen version on
 stable branches

libvirt master might increase its LIBXL_API_VERSION.  When this feeds
through osstest it can cause the push gates of Xen stable branches to
break.

So for stable Xen branches do not track libvirt upstream.  Instead,
use a frozen revision.  (Only for main push gate tests of stable Xen
branches.)

The frozen branch is never going to be updated so it is not suitable
for other kinds of uses.  In particular it won't get security fixes.
So we call the refs   osstest/frozen/xen-K.L-testing  to discourage
users from using them.

Deployment note: The Xen release checklist needs a new item "add this
frozen libvirt branch".

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 cr-daily-branch | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/cr-daily-branch b/cr-daily-branch
index 8b7c789..21780b8 100755
--- a/cr-daily-branch
+++ b/cr-daily-branch
@@ -186,6 +186,12 @@ if [ "x$REVISION_OVMF" = x ]; then
     fi
 fi
 if [ "x$REVISION_LIBVIRT" = x ]; then
+       case "$xenbranch" in
+       xen-[0-9]*-testing)
+               BASE_TAG_LIBVIRT=osstest/frozen/$xenbranch
+               export BASE_TAG_LIBVIRT
+               ;;
+       esac
        determine_version REVISION_LIBVIRT libvirt LIBVIRT
        export REVISION_LIBVIRT
 fi
-- 
2.1.4


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