VM

Virtual Machine Monitor (VMM) (Hypervisor)

• A VMM virtualize an entire physical machine
• VMM controls the hardware, provides an interface to the guest OS, isolates and manange resources among multiple VMs

Hypervisor

Type 1 Hypervisor

1. runs VMM in kernel mode
2. runs guest OS in user mode
3. when a guest OS executes a privileged instruction, it causes a trap to the hypervisor (VMM)
4. VMM emulates the instruction and returns the result to the guest OS (trap-and-emulate)