[fedora-virt] Does this virtual disk exist?

[Tom Horsley <tom horsley att net>]

I've seen all kinds of virtual disk devices for virtual machines
to use, but I was wondering just the other day if this (possibly
silly) sort of virtual disk exists:

Take partitions /dev/sda1, /dev/sdb2, slap together a pretend
MBR and partition table out of thin air, and tell this virtual
machine it is his virtual disk drive.

The motivation being to easily run a virtual machine from
a partition I can also boot as a stand alone separate boot
partition.

Naturally, the initrd stuff would get kind of dicey (hence
the "possibly silly" qualifier :-).