Introduction to Virtual Machines

Administration

• Presentation and class participation: 40%– Each student will present two and a half times this

semester • Full: two papers• Half: One paper (first four weeks)

– Other student read one paper by random assignment

• Project: 60%– A group project starts from week 4

• Two students each group• Choose your own project or discuss with me• Topic settled in week 4• Each group submit a term paper and present in week 14

Presentation Assignment

• Choose one paper from week 2 to 3

• Choose one topic each from each part

Definition

• A virtual machine is an efficient, isolated duplicate of the real machine

• Two categories– System virtual machine– Process virtual machine

System Virtual Machine

• Virtualizing hardware resources: CPU, I/O, memory, networking and GUI– The virtualizing software is called VMM

(virtual machine monitor) or hypervisor

Hardware

VMM

Guest OS

Applications

Hardware

VMM

Guest OS

Applications

Guest OS

Applications

Process Virtual Machine

• A virtual platform that executes an individual process

Hardware

OS

Application Process

Virtualizing software

Virtual Machine Taxonomy

Process VMs System VMs

Same ISA Different ISA

MultiprogrammedSystems

Same-ISA binaryoptimizers

Dynamictranslators

Same ISA Different ISA

ClassicSystemVMs

Host VMs

Whole-SystemVMs

CodesignedVMs

High-level-languageVMs

Why Virtualization: history

• In 1960s, VMM is to use multiplexing mainframe– Why is this important?

• In 1980s and 1990s, VM study became cold– Multitasking OS– Drop in hardware cost

• In 2000s, VM study resurgent– Security, resource utilization, reliability

VMM Characteristics

• Essentially identical– Any program running under VMM shows the

same effect as running on the original machine

• Efficient– No significant decrease in speed

• Resource control– VMM has complete control of resources

Implementation Issues

• CPU

• Memory

• I/O

CPU Virtualization

• A CPU is virtualizable if– It supports direct execution– VMM retains ultimate control of the CPU

• VM runs in unprivileged mode and VMM runs in privileged mode – X86 does not provide a good support– Solution

• Paravirtulization• Full virtualization with binary translation

Memory Virtualization

• Page table– Shadow mechanism

• Memory reallocation– Balloning

• Hardware support

I/O Virtualization

• Challenge of variety of I/O devices– Use hosted VM

• Hardware support– Channel like I/O devices