Linux in a Nutshell, 6th Edition

Virtualization Technology

In full virtualization, the guest operating system doesn’t need to be aware that it is running in a virtual environment. It interacts with the virtual hardware in the same way it would physical hardware. Some tasks in a fully virtualized environment, however, are computationally expensive. One way to handle the expensive tasks is to use a modified processor that performs these tasks for the hypervisor.

Paravirtualization provides another way to handle these expensive tasks. In paravirtualization the guest operating system is modified to hand these expensive tasks to the hypervisor, which can handle the task without having to emulate hardware.