How Hyperlight runs untrusted functions inside hardware-isolated micro virtual machines that start in a millisecond and have no operating system at all.

Welcome to Hyperlight: Micro-VMs Without an Operating System.

Hyperlight is a lightweight virtual machine manager, written in Rust and open-sourced by Microsoft's Azure Core Upstream team as a CNCF sandbox project, that lets an application embed and safely execute untrusted code inside its own process. Its central idea is to push isolation down to the hardware — a real hypervisor boundary around each piece of guest code — while stripping away nearly everything that makes virtual machines slow. There is no guest operating system, no kernel boot, and no device emulation; a Hyperlight guest is a small ELF binary that runs against a slice of memory and a single virtual CPU, and it can be summoned in one to two milliseconds rather than the hundred-plus a conventional VM demands. This book follows that idea from the ground up. The opening chapters explain why ordinary sandboxing forces a choice between speed and safety, and how Hyperlight refuses that trade-off. From there we build up the architecture: the host library that creates and drives VMs, the minimal guest environment that runs inside them, the typed host-guest function calls that cross the hypervisor boundary, and the memory and snapshot machinery that makes reuse cheap. We then turn to hyperlight-wasm, the variant that runs WebAssembly with two layers of sandboxing, before closing with a practical chapter on operating Hyperlight and where it fits in the cloud-native world.

This title is part of the ShriIra library and is free to read in full, right here — our small contribution to making world-class knowledge easy to reach.

A note on reading it: open the Contents menu at the top of the reader to jump between chapters, use the Aa menu to set a comfortable text size, theme (light, sepia, or night), and single- or two-page layout. Your place is saved automatically, so you can always pick up where you left off.

We hope it serves you well.

— Shriira Press

Contents

1. Chapter 1 — The Problem Hyperlight Solves
2. Chapter 2 — Micro-VMs Without an OS
3. Chapter 3 — Architecture and Components
4. Chapter 4 — The Guest Environment
5. Chapter 5 — Host-Guest Function Calls
6. Chapter 6 — Hyperlight Wasm
7. Chapter 7 — Hyperlight in Practice