Update README (#1359)

Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Author: ludfjig

.gitignore

@@ -473,3 +473,4 @@ hyperlight_guest.h
 .gdbinit
 trace/*
 .gdbguest
+.copilot-reviews/

README.md

@@ -1,277 +1,124 @@
 <div align="center">
     <h1>Hyperlight</h1>
     <img src="https://raw.githubusercontent.com/hyperlight-dev/hyperlight/refs/heads/main/docs/assets/hyperlight-logo.png" width="150px" alt="hyperlight logo"/>
-    <p><strong>Hyperlight is a lightweight Virtual Machine Manager (VMM) designed to be embedded within applications. It enables safe execution of untrusted code within <i>micro virtual machines</i> with very low latency and minimal overhead.</strong> <br> We are a <a href="https://cncf.io/">Cloud Native Computing Foundation</a> sandbox project. </p>
+    <p>
+        <strong>A lightweight VMM for running untrusted code in micro VMs with minimal overhead.</strong><br>
+        A <a href="https://www.cncf.io/projects/hyperlight/">Cloud Native Computing Foundation</a> sandbox project.
+    </p>
 </div>
 
-> Note: Hyperlight is a nascent project with an evolving API and no guaranteed support. Assistance is provided on a
-> best-effort basis by the developers.
+> **Status:** Hyperlight is pre-1.0. The API may change between releases, and upgrading will sometimes require code changes.
 
----
-
-## Overview
-
-Hyperlight is a library for creating _micro virtual machines_  — or _sandboxes_ — specifically optimized for securely
-running untrusted code with minimal impact. It supports both Windows and Linux,
-utilizing [Windows Hypervisor Platform](https://docs.microsoft.com/en-us/virtualization/api/#windows-hypervisor-platform)
-on Windows, and either Microsoft Hypervisor (mshv) or [KVM](https://linux-kvm.org/page/Main_Page) on Linux.
-
-These micro VMs operate without a kernel or operating system, keeping overhead low. Instead, guests are built
-specifically for Hyperlight using the Hyperlight Guest library, which provides a controlled set of APIs that facilitate
-interaction between host and guest:
+Hyperlight lets you safely run untrusted code inside hypervisor-isolated micro VMs that spin up in milliseconds, with guest function calls completing in microseconds. You embed it as a library in your Rust application, hand it a guest binary, and call functions across the VM boundary as naturally as calling a local function. To minimize startup time and memory footprint, there's no guest kernel or OS. Guests are purpose-built using the Hyperlight guest library.
 
-- The host can call functions implemented and exposed by the guest (known as _guest functions_).
-- Once running, the guest can call functions implemented and exposed by the host (known as _host functions_).
+- Supports [KVM](https://linux-kvm.org/page/Main_Page), [MSHV](https://github.com/rust-vmm/mshv), and [Windows Hypervisor Platform](https://docs.microsoft.com/en-us/virtualization/api/#windows-hypervisor-platform)
+- No kernel or OS in the VM. Guests are regular ELF binaries written in `no_std` Rust or C
+- Host and guest communicate through typed function calls
+- Guests are sandboxed by default with no access to the host filesystem, network, etc.
 
-By default, Hyperlight restricts guest access to a minimal API. The only _host function_ available by default allows the
-guest to print messages, which are displayed on the host console or redirected to stdout, as configured. Hosts can
-choose to expose additional host functions, expanding the guest’s capabilities as needed.
+## Example
 
-Below is an example demonstrating the use of the Hyperlight host library in Rust to execute a simple guest application.
-It is followed by an example of a simple guest application using the Hyperlight guest library, also written in Rust.
-
-### Host
+**Host** - create a sandbox, register a host function, and call into the guest:
 
 ```rust
-use std::thread;
-
-use hyperlight_host::{MultiUseSandbox, UninitializedSandbox};
-
-fn main() -> hyperlight_host::Result<()> {
-    // Create an uninitialized sandbox with a guest binary
-    let mut uninitialized_sandbox = UninitializedSandbox::new(
-        hyperlight_host::GuestBinary::FilePath("path/to/your/guest/binary".to_string()),
-        None // default configuration
-    )?;
-
-    // Registering a host function makes it available to be called by the guest
-    uninitialized_sandbox.register("Sleep5Secs", || {
-        thread::sleep(std::time::Duration::from_secs(5));
-        Ok(())
-    })?;
-    // Note: This function is unused by the guest code below, it's just here for demonstration purposes
-
-    // Initialize sandbox to be able to call host functions
-    let mut multi_use_sandbox: MultiUseSandbox = uninitialized_sandbox.evolve()?;
-
-    // Call a function in the guest
-    let message = "Hello, World! I am executing inside of a VM :)\n".to_string();
-    // in order to call a function it first must be defined in the guest and exposed so that
-    // the host can call it
-    multi_use_sandbox.call::<i32>(
-        "PrintOutput",
-        message,
-    )?;
-
-    Ok(())
-}
-```
+// Create an uninitialized sandbox by giving it the path to a guest binary.
+// Allocates memory but does not yet run a VM.
+let mut sandbox = UninitializedSandbox::new(GuestBinary::FilePath(guest_path), None)?;
 
-### Guest
+// Register a host function that the guest can call. In a real app this
+// might query a database, read a config, or call an external API.
+// By default, guests can only print to the host.
+sandbox.register("GetWeekday", || Ok("Monday".to_string()))?;
 
-First, create a `Cargo.toml` with the required dependencies:
+// Initialize the sandbox. Starts the VM and runs guest setup code.
+let mut sandbox: MultiUseSandbox = sandbox.evolve()?;
 
-```toml
-[package]
-name = "my-hyperlight-guest"
-version = "0.1.0"
-edition = "2024"
-
-[dependencies]
-hyperlight-guest = "0.12"
-hyperlight-guest-bin = "0.12"
-hyperlight-common = { version = "0.12", default-features = false }
+// Call a function inside the VM
+let greeting: String = sandbox.call("SayHello", "World".to_string())?;
+println!("{greeting}"); // "Hello, World! Today is Monday."
 ```
 
-> **Important:** The `hyperlight-common` crate must have `default-features = false` to avoid pulling in
-> the standard library, which conflicts with the `no_std` requirement for guests.
+Guest state persists across calls. Use `snapshot()` and `restore()` to save and reset VM memory. This avoids recreating the VM while ensuring each call starts from a clean state.
 
-Then, create `src/main.rs`:
+**Guest** (Rust) - declare host functions and expose guest functions with simple macros. Guests can also be [written in C](./src/hyperlight_guest_capi).
 
 ```rust
-#![no_std]
-#![no_main]
-extern crate alloc;
-extern crate hyperlight_guest_bin;
-
-use alloc::vec::Vec;
-use alloc::string::String;
-use hyperlight_common::flatbuffer_wrappers::function_call::FunctionCall;
-use hyperlight_common::flatbuffer_wrappers::guest_error::ErrorCode;
-
-use hyperlight_guest::bail;
-use hyperlight_guest::error::Result;
-use hyperlight_guest_bin::{guest_function, host_function};
-
-#[host_function("HostPrint")]
-fn host_print(message: String) -> Result<i32>;
-
-#[guest_function("PrintOutput")]
-fn print_output(message: String) -> Result<i32> {
-    let result = host_print(message)?;
-    Ok(result)
-}
-
-#[no_mangle]
-pub extern "C" fn hyperlight_main() {
-    // any initialization code goes here
-}
+#[host_function("GetWeekday")]
+fn get_weekday() -> Result<String>;
 
-#[no_mangle]
-pub fn guest_dispatch_function(function_call: FunctionCall) -> Result<Vec<u8>> {
-    let function_name = function_call.function_name;
-    bail!(ErrorCode::GuestFunctionNotFound => "{function_name}");
+#[guest_function("SayHello")]
+fn say_hello(name: String) -> Result<String> {
+    let weekday = get_weekday()?;
+    Ok(format!("Hello, {name}! Today is {weekday}."))
 }
 ```
 
-Build the guest using [cargo-hyperlight](https://github.com/hyperlight-dev/cargo-hyperlight):
+To get started, see the [Getting Started](./docs/getting-started.md) guide. For more details on writing guests, see [How to build a Hyperlight guest binary](./docs/how-to-build-a-hyperlight-guest-binary.md).
 
-```sh
-cargo install --locked cargo-hyperlight
-cargo hyperlight build
-```
-
-> **Note:** You must use `cargo hyperlight build` instead of the regular `cargo build` command.
-> The `cargo-hyperlight` tool sets up the required custom target, sysroot, and compiler flags
-> that are necessary for building Hyperlight guests.
+## When to use Hyperlight
 
-For additional examples of using the Hyperlight host Rust library, see
-the [./src/hyperlight_host/examples](./src/hyperlight_host/examples) directory.
+Hyperlight is a good fit when you need to:
 
-For examples of guest applications, see the [./src/tests/c_guests](./src/tests/c_guests) directory for C guests and
-the [./src/tests/rust_guests](./src/tests/rust_guests) directory for Rust guests.
+- Run untrusted or third-party code with hypervisor-level isolation
+- Create and tear down sandboxes in milliseconds
+- Make guest function calls in microseconds
+- Embed sandboxed execution directly in your application
+- Build functions-as-a-service with hypervisor-level isolation
+- Reuse sandboxes efficiently with snapshot and restore
 
-> Note: Hyperlight guests can be written using the Hyperlight Rust or C Guest libraries.
+Hyperlight is *not* designed for:
 
-## Repository Structure
+- General-purpose virtualization (use a full VMM instead)
+- Running full-blown Linux guest workloads that need syscalls, networking, or filesystem access
 
-- Hyperlight Host Libraries (i.e., the ones that create and manage the VMs)
-    - [src/hyperlight_host](./src/hyperlight_host) - This is the Rust Hyperlight host library.
+## Getting started
 
-- Hyperlight Guest Libraries (i.e., the ones to make it easier to create guests that run inside the VMs)
-    - [src/hyperlight_guest](./src/hyperlight_guest) - The core Rust library for Hyperlight guests. It provides only the essential building blocks for interacting with the host environment, including the VM exit mechanism (`outb`), abstractions for calling host functions and receiving return values, and the input/output stacks used for guest-host communication.
-    - [src/hyperlight_guest_bin](./src/hyperlight_guest_bin/) - An extension to the core Rust library for Hyperlight guests. It contains more opinionated components (e.g., panic handler, heap initialization, musl-specific imports, logging, and exception handling).
-    - [src/hyperlight_guest_capi](./src/hyperlight_guest_capi) - A C-compatible wrapper around `hyperlight_guest_bin`, exposing its core functionality for use in C programs and other languages via FFI.
+See [docs/getting-started.md](./docs/getting-started.md) for detailed prerequisites and platform-specific setup for:
+- **Running** Hyperlight
+- **Building guests**
 
-- Hyperlight Common (functionality used by both the host and the guest)
-    - [src/hyperlight_common](./src/hyperlight_common)
-
-- Test Guest Applications:
-    - [src/tests/rust_guests](./src/tests/rust_guests) - This directory contains three Hyperlight Guest programs written
-      in Rust, which are intended to be launched within partitions as "guests".
-    - [src/tests/c_guests](./src/tests/c_guests) - This directory contains two Hyperlight Guest programs written in C,
-      which are intended to be launched within partitions as "guests".
-
-- Tests:
-    - [src/hyperlight-testing](./src/hyperlight_testing) - Shared testing code for Hyperlight projects built in Rust.
-
-## Try it yourself!
-
-You can run Hyperlight on:
-
-- [Linux with KVM][kvm].
-- [Windows with Windows Hypervisor Platform (WHP).][whp] -  Note that you need Windows 11 / Windows Server 2022 or later to use hyperlight, if you are running on earlier versions of Windows then you should consider using our devcontainer on [GitHub codespaces]((https://codespaces.new/hyperlight-dev/hyperlight)) or WSL2.
-- Windows Subsystem for Linux 2 (see instructions [here](https://learn.microsoft.com/en-us/windows/wsl/install) for Windows client and [here](https://learn.microsoft.com/en-us/windows/wsl/install-on-server) for Windows Server) with KVM.
-- Azure Linux with mshv (note that you need mshv to be installed to use Hyperlight)
-
-After having an environment with a hypervisor setup, running the example has the following pre-requisites:
-
-1. On Linux or WSL, you'll most likely need build essential. For Ubuntu, run `sudo apt install build-essential`. For
-   Azure Linux, run `sudo dnf install build-essential`.
-2. [Rust](https://www.rust-lang.org/tools/install). Install toolchain v1.89 or later.
-3. [just](https://github.com/casey/just). `cargo install just` On Windows you also need [pwsh](https://learn.microsoft.com/en-us/powershell/scripting/install/installing-powershell-on-windows?view=powershell-7.4).
-4. [clang and LLVM](https://clang.llvm.org/get_started.html).
-    - On Ubuntu, run:
-
-        ```sh
-        wget https://apt.llvm.org/llvm.sh
-        chmod +x ./llvm.sh
-        sudo ./llvm.sh 18 clang clang-tools-extra
-        sudo ln -s /usr/lib/llvm-18/bin/ld.lld /usr/bin/ld.lld
-        sudo ln -s /usr/lib/llvm-18/bin/clang /usr/bin/clang
-        ```
-
-    - On Windows, see [this](https://learn.microsoft.com/en-us/cpp/build/clang-support-msbuild?view=msvc-170).
-
-    - On Azure Linux, run:
-
-        ```sh
-        if ! command -v clang > /dev/null 2>&1; then
-            sudo dnf install clang -y
-            sudo dnf install clang-tools-extra -y
-        fi
-        ```
-
-Then, we are ready to build and run the example:
-
-```sh
-just build  # build the Hyperlight library
-just rg     # build the rust test guest binaries
-cargo run --example hello-world
-```
-
-If all worked as expected, you should see the following message in your console:
-
-```text
-Hello, World! I am executing inside of a VM :)
-```
-
-If you get the error `Error: NoHypervisorFound` and KVM or mshv is set up then this may be a permissions issue. In bash,
-you can use `ls -l /dev/kvm` or  `ls -l /dev/mshv` to check which group owns that device and then `groups` to make sure
-your user is a member of that group.
-
-For more details on how to verify that KVM is correctly installed and permissions are correct, follow the
-guide [here](https://help.ubuntu.com/community/KVM/Installation).
-
-For additional debugging tips, including common build and runtime issues, see the [How to build a Hyperlight guest binary](./docs/how-to-build-a-hyperlight-guest-binary.md) guide.
-
-### Or you can use a codespace
+Or skip setup entirely with a codespace:
 
 [![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/hyperlight-dev/hyperlight)
 
-## Contributing to Hyperlight
-
-If you are interested in contributing to Hyperlight, running the entire test-suite is a good way to get started. To do
-so, on your console, run the following commands:
-
-```sh
-just guests  # build the c and rust test guests
-just build  # build the Hyperlight library
-just test # runs the tests
-```
-
-Also , please review the [CONTRIBUTING.md](./CONTRIBUTING.md) file for more information on how to contribute to
-Hyperlight.
-
-> Note: For general Hyperlight development, you may also need flatc (Flatbuffer compiler): for instructions,
-> see [here](https://github.com/google/flatbuffers).
-> Copyright © contributors to Hyperlight, established as Hyperlight a Series of LF Projects, LLC.
-
-## Join our Community Meetings
-
-This project holds fortnightly community meetings to discuss the project's progress, roadmap, and any other topics of interest. The meetings are open to everyone, and we encourage you to join us.
-
-- **When**: Every other Wednesday 09:00 (PST/PDT) [Convert to your local time](https://dateful.com/convert/pst-pdt-pacific-time?t=09)
-- **Where**: Zoom! - Agenda and information on how to join can be found in the [Hyperlight Community Meeting Notes](https://hackmd.io/blCrncfOSEuqSbRVT9KYkg#Agenda). Please log into hackmd to edit!
-
-## Chat with us on the CNCF Slack
-
-The Hyperlight project Slack is hosted in the CNCF Slack #hyperlight. To join the Slack, [join the CNCF Slack](https://www.cncf.io/membership-faq/#how-do-i-join-cncfs-slack), and join the #hyperlight channel.
-
-## More Information
-
-For more information, please refer to our compilation of documents in the [`docs/` directory](./docs/README.md).
-
-## Code of Conduct
-
-See the [CNCF Code of Conduct](https://github.com/cncf/foundation/blob/main/code-of-conduct.md).
-
-[wsl2]: https://docs.microsoft.com/en-us/windows/wsl/install
-
-[kvm]: https://help.ubuntu.com/community/KVM/Installation
+## Repository Structure
 
-[whp]: https://devblogs.microsoft.com/visualstudio/hyper-v-android-emulator-support/#1-enable-hyper-v-and-the-windows-hypervisor-platform
+| Directory | Description |
+|---|---|
+| [src/hyperlight_host](./src/hyperlight_host) | Host library - creates and manages micro VMs |
+| [src/hyperlight_guest](./src/hyperlight_guest) | Core guest library - minimal building blocks for guest-host interaction |
+| [src/hyperlight_guest_bin](./src/hyperlight_guest_bin) | Extended guest library - entry point, panic handler, heap, logging, exceptions |
+| [src/hyperlight_guest_capi](./src/hyperlight_guest_capi) | C API wrapper around `hyperlight_guest_bin` for use via FFI |
+| [src/hyperlight_libc](./src/hyperlight_libc) | C standard library for guests, built from picolibc |
+| [src/hyperlight_guest_macro](./src/hyperlight_guest_macro) | Macros for registering guest and host functions |
+| [src/hyperlight_guest_tracing](./src/hyperlight_guest_tracing) | Tracing support for guests |
+| [src/hyperlight_common](./src/hyperlight_common) | Shared code used by both host and guest |
+| [src/hyperlight_component_macro](./src/hyperlight_component_macro) | Proc macros for WIT-based host/guest bindings |
+| [src/hyperlight_component_util](./src/hyperlight_component_util) | Shared implementation for WIT binding generation |
+| [src/hyperlight_testing](./src/hyperlight_testing) | Shared test utilities |
+| [src/schema](./src/schema) | FlatBuffer schema definitions |
+| [src/trace_dump](./src/trace_dump) | Tool for dumping and visualizing trace data |
+| [src/tests](./src/tests) | Test guest programs (Rust and C) |
+
+## Related Projects
+
+- [cargo-hyperlight](https://github.com/hyperlight-dev/cargo-hyperlight) - Cargo subcommand for building and scaffolding Hyperlight guests
+- [hyperlight-wasm](https://github.com/hyperlight-dev/hyperlight-wasm) - Run WebAssembly modules inside Hyperlight micro VMs
+- [hyperlight-js](https://github.com/hyperlight-dev/hyperlight-js) - Run JavaScript inside Hyperlight micro VMs
+- [hyperlight-sandbox](https://github.com/hyperlight-dev/hyperlight-sandbox) - Multi-backend sandboxing framework for running untrusted code with controlled host capabilities, with Python, .NET, and Rust SDKs
+- [hyperlight-unikraft](https://github.com/hyperlight-dev/hyperlight-unikraft) - Run Linux applications (Python, Node.js, Go, Rust, C/C++) on Hyperlight micro VMs using Unikraft as the guest kernel
+
+## Contributing
+
+See [CONTRIBUTING.md](./CONTRIBUTING.md).
+
+## Community
+
+- **Meetings**: Every other Wednesday 09:00 PST/PDT ([convert to your time](https://dateful.com/convert/pst-pdt-pacific-time?t=09)). Agenda and join info in the [Community Meeting Notes](https://hackmd.io/blCrncfOSEuqSbRVT9KYkg#Agenda).
+- **Slack**: [#hyperlight](https://cloud-native.slack.com/archives/hyperlight) on CNCF Slack ([join here](https://www.cncf.io/membership-faq/#how-do-i-join-cncfs-slack)).
+- **Docs**: [`docs/` directory](./docs/README.md)
+- **Code of Conduct**: [CNCF Code of Conduct](https://github.com/cncf/foundation/blob/main/code-of-conduct.md)
 
+---
 
-## FOSSA Status
 [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fhyperlight-dev%2Fhyperlight.svg?type=large)](https://app.fossa.com/projects/git%2Bgithub.com%2Fhyperlight-dev%2Fhyperlight?ref=badge_large)

docs/README.md

@@ -24,6 +24,7 @@ This project is composed internally of several components, depicted in the below
 
 ## Further reading
 
+* [Getting Started](./getting-started.md)
 * [Glossary](./glossary.md)
 * [How code gets executed in a VM](./hyperlight-execution-details.md)
 * [How to build a Hyperlight guest binary](./how-to-build-a-hyperlight-guest-binary.md)