Hardware virtualization

The x86-based operating systems are designed to run directly on hardware, so they assume that they have full control of the hardware on which they are running.

As discussed, x86 architecture generally offers four levels of privileges, namely Ring 0, Ring 1, Ring 2, and Ring 3, as is described in the following diagram:

These levels of privileges are assigned to operating systems and applications that allow them to manage access to underlying hardware on which they are running. Generally, User Application runs on Ring 3, and the OS must run on Ring 0, which typically has, full privilege over the System Hardware.

Virtualization requires placing a new virtualized layer between the OS and the hardware that will control and manage the guest OS running on top of it, and this is the reason why the virtualization software typically needs higher privileges than that of a guest OS. There are three types of virtualization.