Version 4.0.0 of the QEMU Emulator provides many new features and offers single-processor application developers an open source virtualization emulation tool.

QEMU is a hosted virtual machine monitor. It emulates the machine’s processor to provide a set of different hardware and device models for the machine, allowing it to run various guest operating systems. It can also be used with KVM to run virtual machines at almost native speed.

Source : Qemu