Re: [Xen-devel] Missing libvirt+libxl functionality (Was: Re: [Xen-users] Programmatic administration of Xen machines)

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2016-01-04 at 13:31 +0100, Andreas Pflug wrote:
> Am 04.01.16 um 13:13 schrieb Ian Campbell:
> > On Mon, 2016-01-04 at 12:47 +0100, Andreas Pflug wrote:
> > > Am 04.01.16 um 12:36 schrieb Ian Campbell:
> > > > Sorry to hijack this thread.
> > > > 
> > > > On Mon, 2015-12-28 at 12:56 +0100, Andreas Pflug wrote:
> > > > > Actually, I find virsh a bad idea since its support for the new
> > > > > xl
> > > > > interface isn't feature complete as the old xm interface was. I
> > > > > had
> > > > > to
> > > > > realize this the hard way when my virsh based python tools didn't
> > > > > work
> > > > > as expected after upgrading from xm to xl.
> > > > Note that virsh speaks to libxl directly, not via xl.
> > > > 
> > > > Please can you list the functionality of libvirt's libxl backed
> > > > which
> > > > is
> > > > missing compared to the old xend based one? 
> > > libvirt only handles domains created through it, i.e. using xl at the
> > > same time is incompatible. Since dom0 can't be created using libvirt,
> > > it's missing from "virsh list" in any case.
> > This works for me with a reasonably modern set of bits:
> > 
> > ÂÂÂÂroot@marilith-n0ÂÂÂÂ:~# virsh list
> > ÂÂÂÂÂIdÂÂÂÂNameÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂState
> > ÂÂÂÂ----------------------------------------------------
> > ÂÂÂÂÂ0ÂÂÂÂÂDomain-0ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂrunning
> > ÂÂÂÂÂ13ÂÂÂÂdÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂrunning
> > 
> > It probably requires the correct running of xen-init-dom0 during boot
> > (likely via the xencommons initscript).
> > 
> > I could believe it was broken at some point in history though.
> > 
> > > Âlibvirt stores its own state, not using libxl/xenstore stuff.
> > Please can you elaborate.
> I tested on Debian with 4.4.1 and xl toolstack. See the author's blog
> post:
> https://blog.xenproject.org/2014/01/17/libvirt-support-for-xens-new-
> libxenlight-toolstack/

I think that particular aspect of the blog post is no longer valid, at
least AFAICT with modern libvirt.

> I had even more trouble, e.g. I wasn't able to use non-standard block
> scripts (neither via /etc/xen/scripts/block-XXX nor via a script
> parameter) which are mandatory for me.

Looking at the code it seems like this is still missing.

Copying the devel list and maintainer in case I've either missed something
or there is a reason for this (other than "still on the TODO list", which I
expect is most likely).

If you find other shortcomings of libvirt with libxl then I suppose the
best way to approach them would be to report them as bugs:
    http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen

(I don't know if Jim or libvirt prefers some other means of doing so).

Ian.

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