I recently presented KVM as an efficient virtualization solution for PC's with VMX-enabled processors. Today I present another efficient solution for older processors.
QEMU is a well-known full system emulator, powerful enough to virtualize complete hardware systems. Its major drawback is that it actually emulates the processor, making it unefficient for virtualization purposes when performance is required. The KQEMU kernel module allows QEMU to use the host processor when running on a PC and emulating a PC, removing that performance barrier.