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Virtual Machines. Kenneth Westrom ELEC-6620. Overview. Intro Abstraction versus Virtualization Interfaces Process Virtual Machines System Virtual Machines Conclusion References. Intro. Virtual machines are “an efficient, isolated duplicate of a real machine” -Popek and Goldberg

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virtual machines

Virtual Machines

Kenneth Westrom


Westrom: Virtual Machines

  • Intro
  • Abstraction versus Virtualization
  • Interfaces
  • Process Virtual Machines
  • System Virtual Machines
  • Conclusion
  • References

Westrom: Virtual Machines

  • Virtual machines are “an efficient, isolated duplicate of a real machine”

-Popek and Goldberg

Popek and Goldberg introduced conditions for computer architecture to efficiently support system virtualization.

Westrom: Virtual Machines

abstraction versus virtualization
Abstraction versus Virtualization
  • Computer architecture benefits from Abstraction
    • Well-defined interfaces for hardware and software to use
      • Hard Drives, Networking, I/O devices
    • Limits based on the hardware implementation
  • Virtualization
    • Maps interfaces and

resources to various hardware,

even different architectures

Westrom: Virtual Machines

architecture interfaces
Architecture Interfaces
  • Virtualization can take place at these junctures
    • ISA – Instruction Set Architecture
    • ABI – Application Binary Interface
    • API – Application Programming Interface

Westrom: Virtual Machines

process virtual machines
Process Virtual Machines
  • Also known as Application VM
  • Virtualization below the API or ABI, providing virtual resources to a single process executed on a machine
  • Created for the process alone, destroyed when process finishes

Westrom: Virtual Machines

process vm continued
Process VM, continued
  • Multiprogrammed systems
    • Each application is given effectively separate access to resources, managed by the OS
  • Emulators and translators
    • Executes program binaries compiled for different instruction sets.
    • Slower, requiring hardware interpretation
      • Optimization through storing blocks of converted code for repeated execution

Westrom: Virtual Machines

process vm continued1
Process VM, continued
  • Optimizers, Same ISA
    • Perform code optimization during translation and execution
  • High-level-language VM
    • Cross-platform compatibiltiy
    • Programs written for an abstract machine, which is mapped to real hardware through a virtual machine
      • Sun Microsystems Java VM
      • Microsoft Common Language Infrastructure, .NET framework

Westrom: Virtual Machines

system virtual machines
System Virtual Machines
  • Virtualized hardware below the ISA
  • Single host can run multiple isolated operating systems
    • Servers running different operating systems
    • Isolation between concurrent systems, security
  • Hardware

Managed by the

VMM – Virtual

Machine Manager

Westrom: Virtual Machines

system vm continued
System VM, continued
  • Classically, VMM runs on bare hardware, directly interacting with resources,
    • Intercepts and interprets guest OS actions
  • Hosted VM
    • Installed application that relies on the OS to access hardware, using same ISA
  • Whole System VM
    • Emulate both application and system code for different ISAs
      • Classically: Virtual PC, run windows on old Mac hardware

Westrom: Virtual Machines

system vm continued1
System VM, continued
  • Multiple operating systems on one machine
    • Processor/resources timeshared
    • Quality-of-service isolation
  • Testing of insecure or questionable software and systems
    • Better debugging

Westrom: Virtual Machines

  • Virtual Machines can be useful in crossing boundaries based on ISA differences
  • Hardware consolidation
  • Cross-platform compatability

Westrom: Virtual Machines

  • Smith, Daniel E.; Nair, Ravi. "The Architecture of Virtual Machines". Computer 38 (5): 32–38. IEEE Computer Society.
  • Wikipedia, “Virtual Machine”.

Westrom: Virtual Machines