For example, the requirements for a CPU instruction set, in order for it to be properly virtualizable, had been known in the mainframe computing world for many,

For example, the requirements for a CPU instruction set, in order for it to be properly virtualizable, had been known in the mainframe computing world for many, many years, when Intel and AMD came up with their unvirtualizable (except for VMware‘s heroic tricks) 32 bit instruction sets. Those requirements and their different jargon from the mainframe world were re-discovered from the literature when virtualization in the PC world became a selling point. (Edouard Bugnion et. al. - Hardware and Software Support for Virtualization)