There is quite a bit of documentation on bare metal or Type 1 hypervisors, including my own book, VMware vSphereTM and Virtual Infrastructure Security: Securing the Virtual Environment, but there is not much material on the proper security of hosted environments, or Type 2 hypervisors, such as Microsoft Virtual Server, VMware Workstation, Fusion, Player, or Server as well as Qemu, Virtuozzo, or OpenVZ.