Xen: libvirt.libvirtError: An error occurred, but the cause is unknown

[Mathieu Tarral]

Hi Peter,

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

Le mercredi 7 avril 2021 à 10:56, Peter Krempa <pkrempa at redhat.com> a écrit :

> On Wed, Apr 07, 2021 at 08:14:10 +0000, Mathieu Tarral wrote:
>
> > Hi,
> >
> > I'm facing a strange issue with libvirt and the Xen driver.
> >
> > Whenever I try to define or start a domain, I always get this error:
> >
> > "libvirt.libvirtError: An error occurred, but the cause is unknown" (in Python virt-manager interface)
> >
> > Which is not very helpful.
> >
> > Trying to use virsh directly leads to the same error message:
> >
> > virsh # start win10_xen
> >
> > error: Failed to start domain win10_xen
> >
> > error: An error occurred, but the cause is unknown
>
> This is reported when we fail to set an error message
>
> > I checked /var/log/libvirt/libxl/libxl-driver.log, but the log file is empty.
>
> Please try enabling full debug logging, it may at least show what the
>
> last thing we were doing is.
>
> https://www.libvirt.org/kbase/debuglogs.html#persistent-setting

I enabled the log output in libvirt daemon, and there was one error message that appeared:

error : libxlMakeDomBuildInfo:553 : unsupported configuration: emulator '/usr/lib/xen-4.11/bin/qemu-system-i386' not found

When searching the path with apt-file, there are no packages providing this file.

I have qemu-system-x86-xen however:
https://ubuntu.pkgs.org/20.04/ubuntu-universe-amd64/qemu-system-x86-xen_4.2-3ubuntu6_amd64.deb.html

which provides /usr/bin/qemu-system-i386

Creating a symlink solved my issue:
cd /usr/lib/xen-4.11/bin
sudo ln -s /usr/bin/qemu-system-i386 .

-> This seems to be an opened bug report on the libvirt Debian package (since 2016 !)
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=830307

-> Is there a way for libvirt to actually report meaningful errors in this case ?

Thanks !