Xen-kernel fails to boot (no root device)

[Sladjan Ristic <sladjanri@gmail.com>]

Hi,
    I tried booting into the Xen-kernel in a virtual machine under Hyper-V (Windows 8.1 64bit).
While the normal kernel boots fine, the Xen-kernel cannot find the root device.

Debian6, which doesn't seem to have Hyper-V modules by default, works fine.

Under Debian7 (and testing) I get an error at initramfs (?), which says roughly:
'root device not found'.
When I 'ls' in '/dev', I cannot see any harddrives like 'sda', only the CD-drive seems to be there.

Also, in case it's relevant, there was one message at the start of the boot-process using the
xen-kernel: 'hv_vmbus unable to initialize hypervisor'.

I tried 64bit as well as 32bit Debian guests. Is this a bug to be reported for example, or is
there a solution?

Regards,
Sladi