In the current form, yes HaLVM requires Xen, therefore Xen on ARM support would be required too.
Xen on ARM [1] support is ongoing and from what I can tell, the repository [2] is flagged as unstable therefore certainly still requiring work.
[Edit] RaspberryPi has an ARMv6 CPU. The Xen site reads: "The Xen ARM Project, led by Samsung, is responsible for the direct port of the Xen hypervisor to the ARM processor. So far the focus of the project has been to use Xen Paravirtualization (PV) for a range of processors (ARM v5 - v7).".
This means that it should cover ARMv6 of course. As for the status, I have no idea.