Article by Ajax
To avoid the issues surrounding the non-trappable privileged instructions, CPU manufacturers have added virtualization capabilities to modern CPUs. These CPUs still need to behave exactly like their older counterparts, to ensure backward-compatibility with existing applications, so the behavior of the non-trappable privileged instructions is identical on these newer units. However, a new set of instructions, which were not previously available, provides for a special virtual machine mode of operation. This mode provides extra levels of I/O and memory protection, and allows the special instructions to be detected and handled externally by the CPU in conjunction with a suitably written hyper visor VMM.