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1 Introduction
Warning: Do not run other hypervisors (open-source or commercial virtu-
alization products) together with VirtualBox! While several hypervisors can
normally be installed in parallel, do not attempt to run several virtual ma-
chines from competing hypervisors at the same time. VirtualBox cannot track
what another hypervisor is currently attempting to do on the same host, and
especially if several products attempt to use hardware virtualization features
such as VT-x, this can crash the entire host.
In addition to “plain” hardware virtualization, your processor may also support ad-
ditional sophisticated techniques:
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• A newer feature called “nested paging” implements some memory management
in hardware, which can greatly accelerate hardware virtualization since these
tasks no longer need to be performed by the virtualization software.
On AMD processors, nested paging has been available starting with the
Barcelona (K10) architecture; Intel added support for nested paging, which
they call “extended page tables” (EPT), with their Core i7 (Nehalem) processors.
Nested paging is still disabled by default even for new machines, but it can be
enabled for each virtual machine individually in the machine settings.
If your system supports nested paging (AMD-V) or EPT (VT-x), then you can
expect a significant performance increase by enabling hardware virtualization
and the nested paging feature
• Another hardware feature called “Virtual Processor Identifiers” (VPIDs) can
greatly accelerate context switching by reducing the need for expensive flushing
of the processor’s Translation Lookaside Buffers (TLBs). To enable this feature
for a VM, you need to use the command line; see chapter 8.5, VBoxManage
modifyvm, page 107.
1.3 Features overview
Here’s a brief outline of VirtualBox’s main features:
• Portability. VirtualBox runs on a large number of 32-bit and 64-bit host op-
erating systems (Windows, Linux, Mac OS X and Solaris; see chapter 1.4, Sup-
ported host operating systems, page 16 for details). Virtual machines can easily be
imported and exported using the industry-standard Open Virtualization Format
(OVF, see chapter 3.8, Importing and exporting virtual machines, page 56). Since
the file and image formats used are identical on all the platforms, this works
between all supported host operating systems.
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VirtualBox 2.0 added support for AMD’s nested paging; support for Intel’s EPT and VPIDs was added with
version 2.1.
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