Hardware Support: A Summary

This lesson summarizes the support provided by the hardware for address translation.

Let us now summarize the support we need from the hardware (see figure below).

Privileged mode

First, as discussed in the chapter on CPU virtualization, we require two different CPU modes. The OS runs in privileged mode (or kernel mode), where it has access to the entire machine; applications run in user mode, where they are limited in what they can do. A single bit, perhaps stored in some kind of processor status word, indicates which mode the CPU is currently running in; upon certain special occasions (e.g., a system call or some other kind of ...