These are the low-level interface for Xen on ARM64. Not all of the
interface is included since we don't use all portions of Xen's API.
This was broken off of a "xen/arm64: add xen platform" commit. The
original commit was on the large side, and the hypercall code seemed
distinct from other portions.
A few small adjustments were needed from the original implementation in
Submitted by: Elliott Mitchell <firstname.lastname@example.org>
Original implementation: Julien Grall <email@example.com>, 2014-01-13 17:40:58