- Software-based: Paravirtualization (Xen), binary-translation and emulation (old VMware)
- Hardware-assisted: Uses hardware assisted virtualization technology, HW VT, eg, VT-x and AMD-V (almost any hypervisors)
- vs. emulators/simulators
- Hypervisors run code on real processors (direct execution) plus minimal use of emulation techniques
- Emulators emulate everything; thus, slower
- Many emulators now use HW VT to boost performance: QEMU + KVM, Android Emulator + HAXM, Simics + VMP
- "Hypervisor" is most often interchangeable with "VMM"
- This class will explicitly talk about Hardware-assisted hypervisors