hide the physical hardware – simulate the hardware: virtual machine
allows the execution of multiple OS on the same hardware
hypervisor: manages virtual machine monitors and execute base functions (e.g. scheduling)
full virtualization (e.g., VMWare): include binary translation of non-virtualizable (e.g., privileged instructions in x86) instructions
paravirtualization (e.g., Xen): modify the OS + hyper-calls to the hypervisor to replace non-virtualizable instructions
hardware-assisted virtualization: WM monitor executed in a specific “root” mode + virtualization tasks in hardware + control of the I/O by the hypervisor