Better error message on VM.start when topology is wrong

[olivierlambert]

Hi,

If you start a VM with 8 sockets with 1 core per socket, it will fail with:

INTERNAL_ERROR(xenopsd internal error: File \"ocaml/xenopsd/xc/domain.ml\", line 1125, characters 2-8: Assertion failed)

Would it be possible to get a more obvious error message? Changing the topology to something more sane will work, but we cannot control what users might decide (or we need a way to avoid selecting any configurations).