The architecture of virtual machines

TLDR

Virtual machines can support individual processes or entire systems, providing flexible hardware usage, software isolation, or instruction‑set translation depending on the abstraction level. By virtualizing components such as processors, memory, or I/O devices at a chosen abstraction level and inserting virtualizing software near the hardware/software interface, a VM maps the component’s interface onto that of an underlying system, enabling otherwise incompatible subsystems to work together. Replication through virtualization allows more flexible and efficient use of hardware resources.

Abstract

A virtual machine can support individual processes or a complete system depending on the abstraction level where virtualization occurs. Some VMs support flexible hardware usage and software isolation, while others translate from one instruction set to another. Virtualizing a system or component -such as a processor, memory, or an I/O device - at a given abstraction level maps its interface and visible resources onto the interface and resources of an underlying, possibly different, real system. Consequently, the real system appears as a different virtual system or even as multiple virtual systems. Interjecting virtualizing software between abstraction layers near the HW/SW interface forms a virtual machine that allows otherwise incompatible subsystems to work together. Further, replication by virtualization enables more flexible and efficient and efficient use of hardware resources.