1. Virtual Machines (Introduction to Virtual Machines)
Chihun Kim
Virtual Machines

2. Contents Abstraction, Virtualization of Computer System
Architecture, Implementation Layers
What is VM and Where is VM?
What kind of VM
Process VM
System VM
Example of Complex VM Usage
Rest of the book
Virtual Machines

3. Abstraction, Virtualization of Computer System
Modern computer system is very complex
Hundreds of millions of transisters
Interconnected high-speed I/O devices
Networking infrastructures
Operating systems, libraries, applications
Graphics and networking softwares
To manage this complexity
Levels of Abstractions
seperated by well-defined interfaces
Virtualizations
Virtual Machines

4. Abstraction, Virtualization of Computer System
Levels of Abstraction
Allows implementation details at lower levels of design to be ignored or simplified
Each level is seperated by well-defined interfaces
Design of a higher level can be decoupled from the lower levels
Virtual Machines

5. Abstraction, Virtualization of Computer System
Disadvantage
Components designed to specification for one interface will not work with those designed for another.
Component A
Interface A
Interface A
Component A
Interface B
Component A
Interface B
Virtual Machines

6. Abstraction, Virtualization of Computer System
Similar to Abstraction but doesn’t always hide low layer’s details
Real system is transformed so that it appears to be different
Virtualization can be applied not only to subsystem, but to an Entire Machine → Virtual Machine
Resource A
Resource AA B BB B’
BB’
isomorphism
Virtual Machines

7. Abstraction, Virtualization of Computer System
Applications or OS
Application uses virtual disk as Real disk
Virtualized
Disk
Virtualization
File
File
Abstraction
Real Disk
Virtual Machines

8. Architecture, Implementation Layers
Functionality and Appearance of a computer system but not implementation details
Level of Abstraction = Implementation layer
ISA, ABI, API
Application
Programs
Libraries
Operating System
Execution Hardware
Memory
Translation
IO Devices,
Networking
Controllers
System Interconnect (Bus)
Main Memory
Drivers
Manager
Scheduler
API
ABI
ISA
Virtual Machines

9. Architecture, Implementation Layers
Implementation Layer : ISA
Instruction Set Architecture
Divides hardware and software
Concept of ISA originates from IBM 360
IBM System/360 Model (20, 40, 30, 50, 60, 62, 70, 92, 44, 57, 65, 67, 75, 91, 25, 85, 95, 195, 22) : 1964~1971
Various prices, processing power, processing unit, devices
But guarantee a software compatibility
User ISA and System ISA
Virtual Machines

10. Architecture, Implementation Layers
Implementation Layer : ABI
Application Binary Interface
Provides a program with access to the hardware resource and services available in a system
Consists of User ISA and System Call Interfaces
Virtual Machines

11. Architecture, Implementation Layers
Implementation Layer : API
Application Programming Interface
Key element is Standard Library ( or Libraries )
Typically defined at the source code level of High Level Language
clib in Unix environment : supports the UNIX/C programming language
Virtual Machines

12. What is a VM and Where is the VM?
What is “Machine”?
2 perspectives
From the perspective of a process
ABI provides interface between process and machine
From the perspective of a system
Underlying hardware itself is a machine.
ISA provides interface between system and machine
Virtual Machines

13. What is a VM and Where is the VM?
Machine from the perspective of a process
ABI provides interface between process and machine
Application
Programs
Libraries
Operating System
Execution Hardware
Memory
Translation
IO Devices,
Networking
Controllers
System Interconnect (Bus)
Main Memory
Drivers
Manager
Scheduler
Machine
System calls
User ISA
ABI
Application Software
Virtual Machines

14. What is a VM and Where is the VM?
Machine from the perspective of a system
ISA provides interface between system and machine
Application
Programs
Libraries
Operating System
Execution Hardware
Memory
Translation
IO Devices,
Networking
Controllers
System Interconnect (Bus)
Main Memory
Drivers
Manager
Scheduler
Machine
User ISA
ISA
Application Software
System ISA
Operating System
Virtual Machines

15. What is a VM and Where is the VM?
Virtual Machine is a Machine.
VM virtualizes Machine Itself!
There are 2 types of VM
Process-level VM
System-level VM
VM is implemented as combination of
Real hardware
Virtualizing software
Virtual Machines

16. What is a VM and Where is the VM?
Process VM
VM is just a process from the view of host OS
Application on the VM cannot see the host OS
Guest
Virtualizing
Software
Hardware
System calls
User ISA
ABI
Application Process OS
Runtime
Host
Machine
System calls
User ISA
ABI
Application Software
Virtual
Machine
Virtual Machines

17. What is a VM and Where is the VM?
System VM
Provides a system environment
Machine
User ISA
ISA
Application Software
System ISA
Operating System
Guest
Runtime
Host
Virtualizing
Software
Hardware
Applications OS
Virtual
Machine
Virtual Machines

18. What is a VM and Where is the VM?
System VM
Example of a System VM as a process
VMWare
Other Host Applications
Applications
Virtualizing
Software (VMWare)
Hardware
Host OS
Guest OS
Virtual Machines

19. What kind of VMs Process Virtual Machines System Virtual Machines
Multiprogramming
Emulators and Dynamic Binary Translators
Same-ISA Binary Optimizers
HLL (High Level Language) Virtual Machines
System Virtual Machines
Whole-System Emulations
Codesigned Virtual Machines
Virtual Machines

20. What kind of VMs (Process VM)
(1) Multiprogramming
Process VM
First and most common virtual machine
We don’t think of this as a VM
Each user is given the illusion of having a complete machine
Virtual Machines

21. What kind of VMs (Process VM)
(2) Emulators and Dynamic Binary Translators
Emulates one instruction set on hardware designed for another
As a practical matter, guest and hosts are often the same
Example: FX!32, Aries system
IA-32 Windows Application
Alpha ISA
Windows OS
(for Alpha) VM
Runtime
FX!32 : guest and host have same ISA
Virtual Machines

22. What kind of VMs (Process VM)
Components of Aries system
HP, “PA-RISC to IA-64: Transparent Execution, No Recompilation”, Cindy Zheng, Carol Thompson, IEEE 2000
Program binary for PA-RISC can run on the IA-64 hardware
PA-RISC is a microprocessor architecture developed by HP. “PA” stands for Precision Architecture.
Sometmies, “PA” is considered to stand for “Palo Alto”, the location of HP’s headquaters. (from Wikipedia)
HP PA-RISC 7300LC
Virtual Machines

23. What kind of VMs (Process VM)
Implemented with
Interpreter or Binary Translator
Interpreter
Emulates the execution of individual source instruction
Very slow ( requires 10x processing power )
Binary Translator
Block of source instructions are converted to target instructions
Translated blocks are stored in VM’s memory
Static / dynamic schemes
Virtual Machines

24. What kind of VMs (Process VM)
(3) Same-ISA Binary Optimizers
Source ISA and Target ISA are same
Binary optimizer collects a profile and use this information to optimize application on the fly
Example: HP Dynamo
Virtual Machines

25. What kind of VMs (Process VM)
How HP Dynamo works
HP, “Transparent Dynamo Optimization: The Design and Implementation of Dynamo”, Vasanth Bala, Evelyn Duesterwald, Sanjeev Banerjia, 1999
Virtual Machines

26. What kind of VMs (Process VM)
(4) HLL (High Level Language) Virtual Machines
Main goal is
platform-independence of a application
Full cross-platform portability
Binary class files are distributed
ISA is part of binary class format
Higher level of abstraction
Higher level Virtual ISA
OS is abstracted as standard libraries (API)
Virtual Machines

27. What kind of VMs (Process VM)
Conventional System and HLL VM
Different layer of distribution
HLL Program
Intermediate Code
Object Code
Memory Image
Compiler frontend
Compiler backend
Loader
Distribution
(a) Conventional System
HLL Program
Portable Code
Virtual
Memory Image
Host Instructions
Distribution
Compiler
VM loader
VM Interpreter / Compiler
(b) HLL VM environment
Virtual Machines

28. What kind of VMs (Process VM)
Example : Java
Java Source
Java Binary Classes
Java VM
Implementation
Sparc
Workstation
X86 PC
Apple
Mac
Virtual Machines

29. What kind of VMs (System VM)
(1) Whole-System Emulations
Host and guest systems don’t have a common ISA
Apple PowerPC-based system and Windows PC
Sun servers and Windows PC
Both applications and OS code require emulation
Via binary translation
Example: VMWare
Challenges
If the properties of hardware resources are significantly different
Emulation of ISA features such as virtual memory management or trap handling
Virtual Machines

30. What kind of VMs (System VM)
Example : VMWare
Other Host Applications
Applications
Virtualizing
Software (VMWare)
Hardware
Host OS
Guest OS
Virtual Machines

31. What kind of VMs (System VM)
(2) Codesigned Virtual Machines
Primary goals are
Performance improvement and power efficiency
Uses new ISA and hardware features to execute other ISA
VM is a part of hardware design
Includes a binary translator or dynamic optimizer
Example: Transmeta Crusoe, IBM Daisy
Applications OS
Old ISA
Codesigned VM
New ISA
New hardware
Virtual Machines

32. What kind of VMs (System VM)
Transmeta Crusoe
Transmeta Corp., “The Technology Behind CrusoeTM Processors : Low-power x86-compatible processors implemented with Code MorphingTM software”, Alexdander Klaiber, 2000
Transmeta
Crusoe
Translated from x86 ISA to Crusoe VLIW ISA
by code morphing software
Virtual Machines

33. What kind of VMs (System VM)
IBM Daisy : ISCA’97
Dynamically Architected Instruction Set from Yorktown
Virtual Machines

34. Example of Complex Composition
Crusoe VLIW
Windows IA-32
Linux IA-32
Java Application
JVM
VMWare
Code Morphing
Virtual Machines

35. The Rest of this Textbook
Process VM
Chapter.2
Concepts and Techniques in Emulation
: Emulating ISA and Binary Translation Techniques
Chapter.3
Process VM Architecture and Construction Issues
Chapter.4
Dynamic Optimization
: to improve VM performance
Chapter.5
Architecture of HLL VM
: Popular HLL VM ( Pascal P-code, Java )
Chapter.6
HLL VM Implementation
System VM
Chapter.7
Codesigned VM
: hardware-based performance enhancements
Chapter.8
Conventional System VM
: Basic mechanisms for implementation
Chapter.9
Virtualization issues in Multiprocessor environment
: Partitioning
Bonus
Chapter.10
Future of Virtual Machines
Virtual Machines