hypervisors have been around for quite sometime. the reason they have been difficult for x86 platforms is that you have to go through some contortions to make it work because the instruction set isn't designed to be virtualizable.
the best available example of one that is is the Power and PPC families. get a copy of mol and have at it (just make it run under linux rather than over, but the concept is the same). that said virtualization doesn't really address ISA/architecture emulation. basically it just does for the cpu what virtual memory does for ram.