1. A method for assigning a dedicated hardware device to a Virtual Machine (VM), the method comprising: implementing at least one VM with a guest OS, running under control of a Virtual Machine Monitor (VMM) on a computer system with a host operating system (OS); isolating a hardware device from the host OS; assigning the hardware device to the VM, wherein the VM takes exclusive control of the hardware device by bypassing the VMM when interfacing with the hardware device; the isolation of the hardware device comprising allocation of devices of the computer system so that the host OS operative access to the hardware device is essentially limited, wherein the isolation of the hardware device is provided at boot time by a hypervisor (a) patching of BIOS of the computer system or (b) patching an EFI of the computer system, and wherein the hardware device is visible to the host OS, but becomes inactive for the host OS.