Detecting whether dom0 is in a VM

[George Dunlap <george.dunlap@xxxxxxxxx>]

Hey all,

The following systemd issue was brought to my attention:

https://github.com/systemd/systemd/issues/28113

I think basically, they want `systemd-detect-virt` return the following values:

Xen on hardware, from a dom0:  `none`

Xen on hardware, from a domU: `xen`

Xen in a VM, from a dom0: (ideally the virtualization type, or `vm-other` if not)

Xen in a VM, from a domU: `xen`

Is there a reliable set of tests which would work across all dom0 guest types / architectures?  If not, can we expose the information somehow?

 -George