On 09/15/2015 03:03 PM, Cole Robinson wrote:
> Anyone know how to get fedora + xen running in a KVM VM? I'd like to be able
> to do basic xen/libxl/libvirt testing without needed to reboot a physical 
> machine.
> Trying with F23 AMD host, F22+xen L1, trying to boot into xen in the L1 VM
> just reboots very soon after trying to boot the kernel. Tried disabling all
> virtio for L1 VM, disabling virt extensions for the L1 VM, but it didn't seem
> to change anything. Unfortunately the messages scroll by so quickly I can't
> tell what's happening right before it reboots, and all efforts to convince it
> to print more debugging haven't worked.
> FWIW this does work with rhel5+xen L1, but that's a world away at this point.
> So anyone know if it's even possible? Is there a trick to it? If not,
> suggestions on getting more debug output from xen + grub2?

I've had a tubload of trouble with Xen 4.5 on Fedora 22.  However, you *should* 
be able to boot a Xen hypervisor as a KVM guest.  It requires nested virt on 
the host itself.  I'm not sure if AMD CPUs are capable of doing that, but I've 
had luck with this on Intel Xeons (Nehalem and later).

If F22+Xen as a KVM guest isn't working out, you may need to try F21+Xen as a 
guest and see if that works.

Examples of the trouble I've had with Xen so far:


I usually end up following this page to get some serial output:


Once you get some serial output and prevent Xen from rapidly power cycling, you 
should get something moderately useful for troubleshooting on the graphical or 
serial console.

The noreboot=true and sync_console options might help you troubleshoot, too:


Major Hayden
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