[libvirt] Opinions on removing the old, legacy libvirt Xen driver

[Martin Kletzander]

On Fri, Nov 18, 2016 at 02:25:18PM -0700, Jim Fehlig wrote:
>Hi All,
>
>I briefly mentioned this at an evening event during the KVM Forum / Xen Dev
>Summit, but the list is certainly a better place to discuss such a topic. What
>do folks think about finally removing the old, legacy, xend-based driver from
>the libvirt sources?
>
>The Xen community made xl/libxl the primary toolstack in Xen 4.1. In Xen 4.2, it
>was made the default toolstack. In Xen 4.5, xm/xend was completely removed from
>the Xen source tree. According to the Xen release support matrix [0], upstream
>maintenance of Xen 4.1-4.3 has been dropped for some time, including "long term"
>security support. Xen 4.4-4.5 no longer receive regular maintenance support,
>with security support ending in March for 4.4 and January 2018 for 4.5. In
>short, the fully maintained upstream Xen releases don't even contain xm/xend :-).
>
>As for downstreams, I doubt anyone is interested in running the last several
>libvirt releases on an old Xen installition with xm/xend, let alone libvirt.git
>master. SUSE, which still supports Xen, has no interest in using a new libvirt
>on older (but still supported) SLES that uses the xm/xend toolstack. I struggle
>to find a good reason to keep any of the old cruft under src/xen/. I do think we
>should keep the xm/sexpr config parsing/formatting code src/xenconfig/ since it
>is useful for converting old xm and sexpr config to libvirt domXML.
>
>Thanks for opinions and comments!
>

I'm not familiar with Xen to such detail, particularly with its history,
but allow me to (hopefully) help you with the decision by saying that we
dropped support for any QEmu older than 0.12.0 (released on December
2009).  And by that I don't mean that we stopped fixing bugs for those,
but that libvirt now *mandates* version 0.12.0 or newer.  That is what
is available in CentOS 6 and similar (or as Dan stated it "RHEL-6 era
distros).  For others like me, who don't know when the Xen releases were
made, I found out (for you) that it should be March 2011 for 4.1 and
September that year for 4.2.  So I'm not even going to ask in which
version xl/libxl was introduced.  I think we're totally fine with that
part being removed.  But, please, take it as just an opinion from
someone almost not touched by the Xen areas of the code.

Have a nice day,
Martin

>Regards,
>Jim
>
>[0] https://wiki.xenproject.org/wiki/Xen_Project_Release_Features
>
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