VMR SYSYEM PROCESS

1. Virtual Machines: Versatile Platforms
for Systems and Processes
J. E. Smith
University of Wisconsin-Madison
Ravi Nair
IBM Thomas J. Watson Research Center

2. INTRODUCTION
This material is based on the book, Virtual Machines: Versatile Platforms for
Systems and Processes, Copyright 2005 by Elsevier Inc. All rights reserved.
It has been used and/or modified with permission from Elsevier Inc.

3. Introduction 3
Course Objectives
 Study VM architectures and applications
 Study key implementation technologies
 Focus on architecture and microarchitecture
aspects
 Cover significant case studies

4. Introduction 4
Introduction
Why are virtual machines interesting?
They allow transcending of interfaces
(which often seem to be an obstacle to innovation)
They enable innovation in flexible, adaptive software & hardware,
security, network computing (and others)
They involve computer architecture in a pure sense
Virtualization will be a key part of future computer systems
A fourth major discipline? (with HW, System SW, Application SW)

5. Introduction 5
Advantages of Standard Interfaces
 Major design tasks are decoupled
• In space and time
 Different hardware and software
development schedules
 Software can run on any machine
supporting a compatible interface
PowerPC
MacOS
MacIntosh apps.
x86
Linux
Linux apps
x86
Windows
Windows apps.

6. Introduction 6
There are also disadvantages…
 Software compiled for one ISA will not run on
hardware with a different ISA
• Apple Mac (PowerPC) binaries on an x86?
 Even if ISAs are the same, OSes may differ
• Windows NT applications on a Solaris x86?
 Binary may not be optimized for the specific hardware
platform it runs on
• Intel Pentium 4 binaries on an AMD Athlon?
MacOS
MacIntosh apps
x86 x86
Windows apps.
Linux

7. Introduction 7
Disadvantages (contd.)
 Innovation may be inhibited by fixed ISA
• Hard to add new instructions
OR remove obsolete ones
• What was the most recent (successful) new ISA?
Or new OS?
 Difficult for software to interact directly with
implementation
• Performance features
• Power management
• Fault tolerance
• Software is supposed to be implementation independent

8. Introduction 8
Hardware Resources
 Conventional system software manages
hardware resources directly
• An OS manages the physical memory of a specific
size
• I/O devices are managed as physical entities
 Difficult to share resources except through OS
• All users of hardware must use the same OS
• All users are vulnerable to attack from other users
sharing the resource (via security holes in OS)

9. Introduction 9
Abstraction
 Computer systems are built
on levels of abstraction
 Higher level of abstraction
hide details at lower levels
 Example: files are an
abstraction of a disk
file
file
abstraction
I/O devices
and
Networking
Controllers
System Interconnect
(bus)
Controllers
Memory
Translation
Execution Hardware
Drivers
Memory
Manager
Scheduler
Operating System
Libraries
Application
Programs
Main
Memory
Software
Hardware

10. Introduction 10
Virtualization
 An isomorphism from guest to host
• Map guest state to host state
• Implement “equivalent” functions
Si S
Si
' Sj'
Guest
Host
V(Si) V(Sj)
e(Si)
e'(Si')
j

11. Introduction 11
Virtualization
 Similar to abstraction
Except
• Details not necessarily hidden
 Construct Virtual Disks
• As files on a larger disk
• Map state
• Implement functions
 VMs: do the same thing
with the whole “machine”
file
file
virtualization

12. Introduction 12
Application Program Interface
• API
• User ISA + library calls
The “Machine”
 Different perspectives on
what the Machine is:
 OS developer
 Compiler developer
 Application programmer
Instruction Set Architecture
• ISA
• Major division between hardware
and software
Application Binary Interface
• ABI
• User ISA + OS calls I/O devices
and
Networking
System Interconnect
(bus)
Memory
Translation
Execution Hardware
Application
Programs
Main
Memory
Operating System
Libraries

13. Introduction 13
The “Machine”
 Different perspectives on
what the Machine is:
 OS developer
Instruction Set Architecture
• ISA
• Major division between hardware
and software
I/O devices
and
Networking
System Interconnect
(bus)
Memory
Translation
Execution Hardware
Application
Programs
Main
Memory
Operating System
Libraries

14. Introduction 14
The “Machine”
 Different perspectives on
what the Machine is:
 Compiler developer
Application Binary Interface
• ABI
• User ISA + OS calls
I/O devices
and
Networking
System Interconnect
(bus)
Memory
Translation
Execution Hardware
Application
Programs
Main
Memory
Operating System
Libraries

15. Introduction 15
The “Machine”
 Different perspectives on
what the Machine is:
 Application programmer
Application Program Interface
• API
• User ISA + library calls
I/O devices
and
Networking
System Interconnect
(bus)
Memory
Translation
Execution Hardware
Application
Programs
Main
Memory
Operating System
Libraries

16. Introduction 16
Hardware
"Machine"
OS
Applications
Virtualizing
Software
Virtual
Machine
OS
Applications
Guest
VMM
Host
Virtual Machines
add Virtualizing Software to a Host platform
and support Guest process or system on a Virtual Machine (VM)
Example: System Virtual Machine

17. Introduction 17
The Family of Virtual Machines
 Lots of things are called “virtual machines”
IBM VM/370
Java
VMware
Some things not called “virtual machines”, are virtual machines
IA-32 EL
Dynamo
Transmeta Crusoe

18. Introduction 18
Taking a Unified View
“The subjects of virtual machines and
emulators have been treated as entirely
separate. … they have much in common. Not
only do the usual implementations have many
shared characteristics, but this commonality
extends to the theoretical concepts on which
they are based”
-- Efrem G. Wallach, 1973

19. Introduction 19
Major Program Interfaces
 ISA Interface -- supports all conventional
software
System Calls
User ISA
System ISA
ISA
Application Software
Operating System
System Calls
User ISA
System ISA
ABI
Application Software
Operating System
 Application Binary Interface (ABI)
-- supports application software only

20. Introduction 20
System Virtual Machines
 Provide a system
environment
 Constructed at ISA
level
 Persistent
 Examples: IBM
VM/360, VMware,
Transmeta Crusoe
guest
process
HOST PLATFORM
virtual
network communication
Guest OS
VMM
guest
process
guest
process
guest
process
Guest OS2
VMM
guest
process
guest
process

21. Introduction 21
System Virtual Machines
 Native VM System
• VMM privileged mode
• Guest OS user mode
• Example: classic IBM
VMs
 User-mode Hosted VM
• VMM runs as user
application
 Dual-mode Hosted VM
• Parts of VMM privileged;
parts non-privileged
• Example VMware
Non-privileged
modes
Privileged
Mode
Virtual
Machine
VMM
Hardware
Virtual
Machine
Host OS
Hardware
VMM
Virtual
Machine
Host OS
Hardware
VMM

22. Introduction 22
Process VMs
 Execute application binaries with an ISA different from
hardware platform
 Couple at ABI level via Runtime System
 Examples: IA-32 EL, FX!32
Virtualizing
Software
Application Process
Machine
OS
Hardware
Guest
Runtime
Host
Application Process
Virtual
Machine

23. Introduction 23
Process Virtual Machines
 Constructed at ABI level
 Runtime manages guest
process
 Not persistent
 Guest processes may
intermingle with host
processes
 As a practical matter, guest
and host OSes are often
the same
 Dynamic optimizers are a
special case
 Examples: IA-32 EL, FX!32,
Dynamo
HOST OS
Disk
file sharing
network communication
guest
process
create
host
process
guest
process
runtime
runtime
guest
process
runtime
host
process

24. Introduction 24
Same-ISA Dynamic Binary Optimizers
 Optimize Binary at Runtime
 An ABI level optimization
 A type of Process VM
 Example HP Dynamo
• Can optimize for dynamic
properties of program
• Can optimize for a specific
processor implementation
HP PA
UNIX
HP Apps

25. Introduction 25
HLL VMs
 Java and CLI are recent examples
 Binary class files are distributed
 “ISA” is part of binary class format
 OS interaction via APIs (part of VM platform)
Sparc
Workstation
Java Binary Classes
x86
PC
Apple
Mac
VM
implementation
VM
implementation
VM
implementation
Java VM
Architecture

26. Introduction 26
High Level Language Virtual Machines
 Raise the level of abstraction
• User higher level virtual ISA
• OS abstracted as standard libraries
 Process VM (or API VM)
HLL Program
Intermediate Code
Memory Image
Object Code
(ISA)
Compiler front-end
Compiler back-end
Loader
HLL Program
Portable Code
(Virtual ISA )
Host Instructions
Virt. Mem. Image
Compiler
VM loader
VM Interpreter/Translator
Traditional HLL VM

27. Introduction 27
Co-Designed VMs
VLIW
Windows
X86 Apps
 Perform both translation and
optimization
 VM provides interface between
standard ISA software and
implementation ISA
 Primary goal is performance or
power efficiency
 Use proprietary implementation ISA
 Transmeta Crusoe and IBM Daisy
best-known examples

28. Introduction 28
Composition
ISA 2
OS 1
apps 2
OS 1
apps 1

29. Introduction 29
Composition: Example
Java application
Linux x86
JVM
Windows x86
VMware
Crusoe VLIW
Code Morphing

30. Introduction 30
Summary (Taxonomy)
VM type (Process or System)
Host/Guest ISA same or different
Multiprogrammed
Systems
Java VM
MS CLI
Transmeta
Crusoe
same ISA
different
ISA
Process VMs System VMs
Virtual PC
for Mac
different
ISA
same ISA
IBM VM/370
VMware
HP
Dynamo
IA-32 EL
FX!32

31. Introduction 31
Course Topics
 Introduction & VM Overview
 Emulation: Interpretation & Binary Translation
 Process VMs & Dynamic Translators
 Dynamic Binary Optimization
 Co-Designed VMs
 HLL VMs
 System VMs
 Emerging Applications

32. Introduction 32
Case Studies
 Shade
 Sun WABI
 Compaq FX!32
 HP Dynamo
 VMware
 Transmeta Crusoe
 IBM Daisy
 Intel VT-x
…. and others