Authors (if Research)
Havard K.F. Bjerke
July 18, 2005; Master's Thesis
The Xen Virtual Machine Monitor has proven to achieve higher efficiency in
virtualizing the x86 architecture than competing x86 virtualization technologies.
This makes virtualization on the x86 platform more feasible in High-
Performance and mainframe computing, where virtualization can offer attractive
solutions for managing resources between users. Virtualization is also attractive
on the Itanium architecture. Future x86 and Itanium computer architectures
include extensions which make virtualization more efficient. Moving to virtualizing
resources through Xen may ready computer centers for the possibilities
offered by these extensions.
The Itanium architecture is “uncooperative” in terms of virtualization. Privilege-
sensitive instructions make full virtualization inefficient and impose the
need for para-virtualization. Para-virtualizing Linux involves changing certain
native operations in the guest kernel in order to adapt it to the Xen virtual architecture.
Minimum para-virtualizing impact on Linux is achieved by, instead
of replacing illegal instructions, trapping them by the hypervisor, which then
emulates them. Transparent para-virtualization allows the same Linux kernel
binary to run on top of Xen and on physical hardware.
Itanium region registers allow more graceful distribution of memory between
guest operating systems, while not disturbing the Translation Lookaside Buffer.
The Extensible Firmware Interface provides a standardized interface to hardware
functions, and is easier to virtualize than legacy hardware interfaces.
The overhead of running para-virtualized Linux on Itanium is reasonably
small and measured to be around 4.9 %. Also, the overhead of running transparently
para-virtualized Linux on physical hardware is reasonably small compared
to non-virtualized Linux.