[Pkg-xen-devel] Does it still make sense to have versioned xen-hypervisor, libxen and xen-utils?

[Bastian Blank]

On Wed, Feb 18, 2015 at 02:53:07PM +0100, Stefan Bader wrote:
> - libvirt
>   * 1.2.12 starts to validate configs and requires full path specifications
>     for hvmloader, pygrub, and qemu. Things are not completely cleared up,
>     yet. But for the future the xen build would create a xenlight.pc that
>     communicates the used paths. But still this would require to rewrite
>     configuration files when switching between versioned libxl.

So libvirt is broken in this respect.

>   * Even now there is only one libvirt which is compiled against one version
>     of libxl. At least when moving between xen 4.4 and 4.5 this caused issues.
>     Libvirtd would fail to start as long as it was not recompiled against libxl
>     4.5. I have not tested the other way round but it probably is as bad.

And this would not change with unversioned utils, as the libs still have
versions.

> - qemu
>   * That qemu also is compiled against one version of libxl. When moving from
>     4.4 to 4.5 without recompiling qemu the issues were subtle. Not sure why
>     but using cirrus on HVM would stop updating a VNC screen as soon as the
>     resolution was changed.

$ ldd /usr/bin/qemu-system-x86_64 | grep xen
        libxenstore.so.3.0 => /usr/lib/x86_64-linux-gnu/libxenstore.so.3.0 (0x00007f401610c000)
        libxenctrl-4.4.so => /usr/lib/x86_64-linux-gnu/libxenctrl-4.4.so (0x00007f4015ee4000)
        libxenguest-4.4.so => /usr/lib/x86_64-linux-gnu/libxenguest-4.4.so (0x00007f4015cb8000)

Neither libvirt nor qemu are critical for the system.

> So given that for above reasons moving between xen versions installed in
> parallel is not as straight forward as one would hope and maintaining the
> patches to get the versioned packages is some effort, what are/were the reasons
> to do this? Might be a dumb question but I guess I have to ask anyway.

The same reason why the name of the kernel changes now and then.  And
yes, I use this with Xen 4.1, 4.4 and 4.5 on several machines.

Bastian

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