QEMU is a FAST! processor emulator

QEMU is a generic and open source processor emulator which achieves a good
emulation speed by using dynamic translation. QEMU has two operating modes:

 * Full system emulation. In this mode, QEMU emulates a full system (for
   example a PC), including a processor and various peripherials. It can be
   used to launch different Operating Systems without rebooting the PC or
   to debug system code.
 * User mode emulation. In this mode, QEMU can launch Linux processes compiled
   for one CPU on another CPU.

As QEMU requires no host kernel patches to run, it is safe and easy to use.