Introduction to Virtual Machines
Overview
Types of Virtualization
Starting Point: A Physical Machine
What is a Virtual Machine?
Virtualization Properties
What is a Virtual Machine Monitor?
Classic Virtualization and Applications
Modern Virtualization Renaissance
Modern Virtualization Applications
Processor Virtualization
Trap and Emulate
“Strictly Virtualizable”
Issues with Trap and Emulate
Binary Translation
Issues with Binary Translation
Memory Virtualization
Traditional Address Spaces
Traditional Address Translation
Virtualized Address Spaces
Virtualized Address Spaces w/ Shadow Page Tables
Virtualized Address Translation w/ Shadow Page Tables
Issues with Shadow Page Tables
Virtualized Address Spaces w/ Nested Page Tables
Virtualized Address Translation w/ Nested Page Tables
Issues with Nested Page Tables
Interposition with Memory Virtualization Page Sharing
I/O Virtualization
I/O Virtualization Implementations
Issues with I/O Virtualization
Brief History of VMware x86 Virtualization
Passthrough I/O Virtualization

Issues with Nested Page Tables

Positives
Simplifies monitor design
No need for page protection calculus
Negatives
Guest page table is in physical address space
Need to walk PhysMap multiple times
Need physical-to-machine mapping to walk guest page table
Need physical-to-machine mapping for original virtual address
Other Memory Virtualization Hardware Assists
Monitor Mode has its own address space
No need to hide the VMM