Introduction to Address Translation
Explore the fundamentals of address translation and how hardware and operating systems collaborate to create efficient, flexible, and secure virtual memory. Understand limited direct execution, hardware-based address translation, and how the OS controls memory access to ensure each program operates within its own protected address space.
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Limited direct execution
In developing the virtualization of the CPU, we focused on a general mechanism known as limited direct execution (or LDE). The idea behind LDE is simple: for the most part, let the program run directly on the hardware; however, at certain key points in time (such as when a process issues a system call, or a timer interrupt occurs), arrange so that the OS gets involved and makes sure the “right” thing happens. Thus, the OS, with a little hardware support, tries its best to get out of the way of the running program, to deliver an efficient virtualization; however, by interposing at those critical points in time, the OS ensures that it maintains control over the ...