
3 Configuring virtual machines
You can select for each virtual machine individually whether VirtualBox should use software or hardware virtualization. Prior to VirtualBox version 2.2, software virtu- alization was the default; starting with version 2.2, VirtualBox will enable hardware virtualization by default for new virtual machines that you create. (Existing virtual machines are not automatically changed for compatibility reasons, and the default can of course be changed for each virtual machine.)
Even though VirtualBox does not always require hardware virtualization, enabling it is required in the following scenarios:
•Certain rare guest operating systems like OS/2 make use of very esoteric pro- cessor instructions that are not supported with our software virtualization. For virtual machines that are configured to contain such an operating system, hard- ware virtualization is enabled automatically.
•VirtualBox’s
The reason for changing the default with version 2.2 is that the hardware has sig- nificantly improved with the latest Intel and AMD processors, and VirtualBox has also
Warning: Do not run other hypervisors
In addition to “plain” hardware virtualization, your processor may also support ad- ditional sophisticated techniques:2
•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.
2VirtualBox 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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