Preface
Virtual machine (VM) technologies have been developed in a number of
contexts ~ operating systems, programming languages and compilers, and
computer architecture ~ to enable new capabilities and to solve a variety of
problems in interfacing major computer system components. Virtual machines
for supporting operating systems are receiving renewed interest after years of
relatively little activity, because they allow effective resource sharing while
maintaining a high degree of security. Virtualization is becoming popular for
servers and other network applications especially where security is of crucial
importance. In the area of programming languages, virtual machines provide
platform independence, and they support transparent dynamic translation and
optimization. In processor architectures, virtual machine technologies allow
the introduction of new instruction sets, as well as dynamic optimization for
power reduction and/or performance improvement.
Because of industry consolidation around a small number of standard inter-
faces, virtual machine technology will likely be an important enabling feature
for innovations in all of the above fields. Any new instruction set, oper-
ating system, or programming language will almost certainly require some
accompanying virtual machine technology if it is to become widely accepted.
Not coincidentally, much of the impetuses for virtual machine technolo-
gies, and most of the more significant recent developments, have come from
industry.
Historically, the various VM techniques have been spread across computer
science and engineering disciplines. However, there are a number of under-
lying, cross-cutting technologies, and there is much to be gained by pulling
them together so that VM implementations can be studied and engineered
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