In part 1 of this series, I introduced the concepts of full virtualization and paravirtualization (PV), as well as the hardware virtualization (HVM) feature used by Xen (among other things) to implement full virtualization. I also introduced the concept of installing paravirtualized drivers on a fully virtualized system. This small step, from full virtualization towards paravirtualization, begins to hint at the idea of a spectrum of paravirtualization. In this article, I will cover the historical reasons for the development of PVHVM, and finally of the newest mode, PVH.




