Re: [Xen-devel] OT: xen libvirt issue

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 8 Apr 2013, Jim Fehlig wrote:
> AL13N wrote:
> > Op maandag 8 april 2013 06:22:49 schreef Marek Marczykowski:
> >   
> >> On 05.04.2013 13:13, George Dunlap wrote:
> >>     
> >>> On Fri, Apr 5, 2013 at 9:21 AM, Dario Faggioli
> >>>
> >>> <dario.faggioli@xxxxxxxxxx> wrote:
> >>>       
> >>>> On gio, 2013-04-04 at 21:49 +0200, AL13N wrote:
> >>>>         
> >>>>> i realise this is completely off-topic, but if someone on this list has
> >>>>> some knowledge on this, see:
> >>>>>
> >>>>> https://www.redhat.com/archives/libvir-list/2013-April/msg00189.html
> >>>>>
> >>>>> the issue is that shutting down xen domains, segfaults libvirtd... which
> >>>>> is
> >>>>> annoying
> >>>>>           
> >>>> I don't have any clue on this... But, perhaps, Jim does (Cc-ing him)?
> >>>>         
> >>> The e-mail that AL13N linked to was actually from Jim, saying he would
> >>> be really busy for a while and unable to look at it.
> >>>
> >>> The question isn't off-topic, as libxl and xend have to work closely
> >>> with libvirt.  Unfortunately, I don't think any of the active
> >>> developers on this list has much familiarity with libvirt.  It Would
> >>> Be Good if someone could step up and learn, but with our feature
> >>> freeze next week, we're also kind of heads-down getting stuff
> >>> implemented...
> >>>       
> >> I believe it is already fixed in unstable by this commit:
> >> 5f5ef65babc2ca15f43b775c4b47b0102fa2a632 "libxl: fix stale timeout event
> >> callback race"
> >>
> >> Sadly backport to 4.2 isn't trivial.
> >>     
> >
> > Looking at the patch i totally agree that it isn't trivial...
> >   
> 
> It will certainly help, but I've heard reports there are still problems
> even with that patch.  IIRC, Bamvor has seen a similar segfault using
> git master of libvirt and xen-unstable, although it is a bit harder to
> trigger.
 
Do you have a link to a bug report somewhere?


> I think we need to rework the code for handling shutdown events.  The
> current code worked with libxl in Xen 4.1, but has proven to be racy
> with libxl in Xen 4.2.  I plan to work on this, but unfortunately not
> for a few weeks.  I'm busy with another project this week and will be
> traveling the week of April 15.

I realize that it actually takes time but it would be great if you could
write down in a bit more details the proposed fix, in case somebody else
volunteers to fix the issue in the meantime.


> > i'll hold off for now. and will work more towards libvirt integration for 
> > Mageia 4 (our release freeze is now in effect for Mageia 3).
> >   
> 
> FYI, although it is deprecated, the xm/xend toolstack works well with
> Xen 4.2, and the legacy libvirt xen driver is quite stable.  It was the
> first hypervisor driver in libvirt  :).

The problem is that xend doesn't support upstream QEMU as a disk
backend, and the status of blktap in most distros is pretty poor.

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