Virtual Machine

Virtual Machine

1. OS needs to securely multiplex resources by protecting applications from each other while also sharing physical resources between them.

2. Share CPU, each application gets virtual processor

   • Processes run on virtual processor
     • Each process has state maintained by OS, New, Running, Ready, Blocked and Exit
   • Each process assigned a process control block (PCB), where information about it is stored, including unique process identifier, the current state, PC and CPU registers, CPU scheduling information, memory management...
     • For OS to switch context between processes, needs to store current data from process in its own PCB, and then load the new data from the second process' PCB.

3. Allocate and Protect memory, virtual address spaces for each application

4. Present set of hardware independent virtual devices

5. Divide up storage space with filing systems.

6. Process Concepts

   • A process is a program in execution
     • programs are static while processes are dynamic
     • Includes PC, stack and data section