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

[Jim Fehlig]

On 4/7/21 3:25 AM, Mathieu Tarral wrote:
> 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

libxlMakeDomBuildInfo reports the error via virReportError

https://gitlab.com/libvirt/libvirt/-/blob/master/src/libxl/libxl_conf.c#L592

> 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 ?

A meaningful error is reported, it's just not making it back to the client. And 
I don't spot anywhere along the failure path of libxlDomainCreateWithFlags -> 
libxlDomainStartNew -> libxlDomainStart -> libxlMakeDomBuildInfo where that 
helpful error would be unset/overwritten.

Regards,
Jim