cloud-hypervisor/docs/releases.md

Release Documentation

Abstract

This document provides guidance to users, downstream maintainers and any other consumers of the Cloud Hypervisor project, this document describes the release process, release cadence, stability expectations and related topics.

Basic Terms

Stability

For Cloud Hypervisor the following areas are subject to stability guarantees:

• REST API
• Command line options
• Device Model
• Device tree, device list, ACPI, Hyper-V enlightenments and any other features exposed to guest
• KVM compatibility
• Rust edition compatibility

This list is incomplete but this document serves as a best effort guide to stability across releases.

Experimental features

Experimental features are under active development and no guarantees are made about their stability.

List of experimental features:

• TDX
• vfio-user
• vDPA

Security

Security fixes should be included in a new point release.

For security issues an advisory will be published via the GitHub security advisory process along with the release. Watching the project on GitHub will notify you of those issues.

Releases

Versioning

The versioning scheme uses MAJOR.POINT pattern:

• MAJOR can introduce incompatible changes along with support for new features. Changes to the API, CLI options and device model require a notice at least 2 releases in advance for the actual change to take place.
• POINT contains bug fixes and/or security fixes.

Major Release Cadence

Cloud Hypervisor is under active development. A new major release is issued approximately every 6 weeks. Point releases are issued on demand, when important bug fixes are in the queue. A major release would receive bug fixes for the next two cycles (~12 weeks) and then be considered EOL.

+ - Active release support
E - EOL

        2021                2022                2023 
         |    |    |    |    |    |    |    |    | 
18.0     |    |    |  ++++++++E
19.0     |    |    |    |++++++++E
20.0     |    |    |    |   ++++++++E
21.0     |    |    |    |    | ++++++++E
22.0     |    |    |    |    |    +++++++++E
23.0     |    |    |    |    |    |  +++++++++E

Major Release Stability Considerations

Snapshot/restore support is not compatible across MAJOR versions. Live migration support is not compatible across MAJOR versions.

LTS Release Cadence

A regular release is promoted to LTS every 12 months. An LTS release is supported for 18 months. This gives a 6 months window for users to move to the new LTS.

+ - Active release support
E - EOL

        2022                2023               2024                 2025                2026
         |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |
23.0     |    |+++++++++++++++++++++++++++++E
43.0     |    |    |    |    |    |+++++++++++++++++++++++++++++E
63.0     |    |    |    |    |    |    |    |    |    |+++++++++++++++++++++++++++++E

LTS Stablity Considerations

An LTS release is just a MAJOR release for which point releases are made for longer following the same rules for what can be backported to a POINT release. The focus lays on critical and security bug fixes which are pulled at the maintainer's discretion.