Hi,
I tried booting Xen-kernel 4.3 in a Hyper-V virtual machine. The vm runs Debian7, which uses hv modules for Hyper-V. When I boot the normal kernel, it is fine, but booting Debian's xen-kernel doesn't work, because no virtual disk drives can be found. This looks like an issue with the hv modules, because without them, the xen-kernel boots fine. I tested this by using an older Debian6, where hv modules are not loaded by default.
Regards,
Sladi