kata-containers/docs/hypervisors.md
James O. D. Hunt 4f0726bc49 docs: Remove table of contents
Removed all TOCs now that GitHub auto-generates them.

Also updated the documentation requirements doc removing the requirement
to add a TOC.

Fixes: #2022.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
2021-07-30 10:58:22 +01:00

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# Hypervisors
## Introduction
Kata Containers supports multiple hypervisors. This document provides a very
high level overview of the available hypervisors, giving suggestions as to
which hypervisors you may wish to investigate further.
> **Note:**
>
> This document is not prescriptive or authoritative:
>
> - It is up to you to decide which hypervisors may be most appropriate for
> your use-case.
> - Refer to the official documentation for each hypervisor for further details.
## Types
Since each hypervisor offers different features and options, Kata Containers
provides a separate
[configuration file](/src/runtime/README.md#configuration)
for each. The configuration files contain comments explaining which options
are available, their default values and how each setting can be used.
> **Note:**
>
> The simplest way to switch between hypervisors is to create a symbolic link
> to the appropriate hypervisor-specific configuration file.
| Hypervisor | Written in | Architectures | Type | Configuration file |
|-|-|-|-|-|
[ACRN] | C | `x86_64` | Type 1 (bare metal) | `configuration-acrn.toml` |
[Cloud Hypervisor] | rust | `aarch64`, `x86_64` | Type 2 ([KVM]) | `configuration-clh.toml` |
[Firecracker] | rust | `aarch64`, `x86_64` | Type 2 ([KVM]) | `configuration-fc.toml` |
[QEMU] | C | all | Type 2 ([KVM]) | `configuration-qemu.toml` |
## Determine currently configured hypervisor
```bash
$ kata-runtime kata-env | awk -v RS= '/\[Hypervisor\]/' | grep Path
```
## Choose a Hypervisor
The table below provides a brief summary of some of the differences between
the hypervisors:
| Hypervisor | Summary | Features | Limitations | Container Creation speed | Memory density | Use cases | Comment |
|-|-|-|-|-|-|-|-|
[ACRN] | Safety critical and real-time workloads | | | excellent | excellent | Embedded and IOT systems | For advanced users |
[Cloud Hypervisor] | Low latency, small memory footprint, small attack surface | Minimal | | excellent | excellent | High performance modern cloud workloads | |
[Firecracker] | Very slimline | Extremely minimal | Doesn't support all device types | excellent | excellent | Serverless / FaaS | |
[QEMU] | Lots of features | Lots | | good | good | Good option for most users | | All users |
For further details, see the [Virtualization in Kata Containers](design/virtualization.md) document and the official documentation for each hypervisor.
[ACRN]: https://projectacrn.org
[Cloud Hypervisor]: https://github.com/cloud-hypervisor/cloud-hypervisor
[Firecracker]: https://github.com/firecracker-microvm/firecracker
[KVM]: https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine
[QEMU]: http://www.qemu-project.org