1. A method for assigning a hardware device to a Virtual Machine (VM), the method comprising: on a computer system with a host operating system (OS) and a Virtual Machine Monitor (VMM), implementing at least one VM running under control of the VMM; giving the VM exclusive control of the hardware device by bypassing the VMM when the VM interfaces with the hardware device; and isolating the hardware device by modifying allocation of devices of the host OS at boot time so that the host OS sees the hardware device as inactive, wherein the isolating is provided by (a) patching of BIOS of the computer system or (b) patching an EFI of the computer system.