Before revision: Virtualization theorems To derive their virtualization theorems, which give sufficient (but not necessary) conditions for virtualization, Popek and Goldberg introduce a classification of instructions of an ISA into 3 different groups: Privileged instructions Those that trap if the processor is in user mode and do not trap if it is in system mode (supervisor mode).
After revision: someVirtualization theorems To derive their virtualization theorems, which give sufficient (but not necessary) conditions for virtualization, Popek and Goldberg introduce a classification of instructions of an ISA into 3 different groups: Privileged instructions Those that trap if the processor is in user mode and do not trap if it is in system mode (supervisor mode).