# Optimized, libvirt-compatible definitions for common OS

## Goal

This repository's goal is to maintain definitions that are tuned for running modern, GUI-driven guest operating systems (OS), easing their installation on hosts that leverage KVM, such as [Phyllome OS](https://phyllo.me/).

There are two kinds of definition for QEMU: **session-driven** virtual machines, and **system-driven** virtual machines. System-driven virtual machines are running with higher privileges. If one intend to share a physical device with a virtual machine using VFIO passthrough, this is the definition to use. More information [here](https://blog.wikichoon.com/2016/01/qemusystem-vs-qemusession.html).

## Usage

### Requirements

It is expected that libvirt and other dependencies such as QEMU or the Cloud Hypervisor are already installed and correctly configured.

* At least `QEMU` emulator version 7.0.0
* At least `libvirt` 8.6.0
* [Netboot.xyz](https://netboot.xyz/) ISO file under `/var/lib/libvirt/isos`

### How to use it

* Download `Netboot.xyz.iso` file

```
# wget https://boot.netboot.xyz/ipxe/netboot.xyz.iso -P /var/lib/libvirt/isos/
```

* Clone this repository

* Navigate to the *session* directory

* Choose your target OS of choice and, as a normal user, use the following `virsh` command to create a virtual machine using the `define` argument:

```
$ virsh define linux54.xml
Domain 'Linux5.4' defined from linux54.xml
```

* List the newly-created virtual machine

```
$ virsh list --all
 Id   Name       State
------------------------
 -    Linux5.4   shut off
```

* Delete the virtual machine usine the `undefine` argument

```
$ virsh undefine Linux5.4
Domain 'Linux' has been undefined
```

### System-driven virtual machines

* Navigate to the *system* directory

* Choose your target OS of choice and, as a root user, use the following `virsh` command to define a virtual machine:

```
# virsh define linux54.xml
Domain 'Linux5.4' defined from linux54.xml
```

```
# virsh list --all
 Id   Name       State
------------------------
 -    Linux5.4   shut off
```

* Delete it

```
# virsh undefine Linux5.4
Domain 'Linux5.4' has been undefined
```

## Status

|     | Linux 5.4 | Linux 5.15 | Windows 10 | Windows 11 |
| --- | --- | --- | --- | --- |
| *Chipset* | `Q35` | `Q35` | `Q35` | `Q35` |
| *Platform Firmware* | `OVMF` | `OVMF` | `OVMF` | `OVMF` |
| *Secure boot* | No  | No  | No  | **Yes** |
| *[Netboot.xyz](https://netboot.xyz/) ISO loaded* | **Yes** | **Yes** | **Yes** | No |
| *`Spice display`* | **Yes**, with 3D accel. | **Yes**, with 3D accel. | **Yes**, without 3D accel. | **Yes**, without 3D accel. |
| *`virtio-gpu`* | **Yes**, with 3D accel. | **Yes**, with 3D accel. | **Yes**, without 3D  accel. | **Yes**, without 3D  accel. |
| *`virtio-blk`* | Not applicable | Not applicable | Not applicable | Not applicable |
| *`virtio-scsi`* | **Yes** | **Yes** | **Yes** | **Yes** |
| *`virtio-fs`* | **Yes**, for System-driven VM | **Yes**, for System-driven VM | **Yes** | **Yes** |
| *`virtio-net`* | **Yes** | **Yes** | **Yes** | **Yes** |
| *`virtio-keyboard`* | **Yes** | **Yes** | **Yes** | **Yes** |
| *`virtio-tablet`* | **Yes** | **Yes** | **Yes** | **Yes** |
| *`virtio-iommu`* | No | **Yes** | No | No |

More information [here](https://wiki.phyllo.me/e/en/virt/guest) on the status for virtio support on guest operating systems.

## Context

[Libvirt](https://libvirt.org/) is the most popular virtualization library on Linux, and it is central to Phyllome OS.

Libvirt uses an XML file to store the definition of a virtual machine, including its firmware (e.g. BIOS or UEFI-based), the size of its memory, the nature of a particular device (e.g. virtio or emulated hardware), etc.

### Why

[The reference Domain XML format webpage](https://libvirt.org/formatdomain.html), which is almost 100 pages long, lists most of the accepted parameters that can be used to define a virtual machine. 

Picking the most optimized parameters for running a particular guest OS is a complicated task. This project intends to find the best parameters for the most popular OS.

### Assomptions 

The best parameters are defined as parameters that are: 
- Performance-oriented, providing good out-of-the-box performance.
- Relatively host-agnostic, so that a virtual machine could be migrated to another host. 
- Modern, leveraging as many paravirtualized devices (a.k.a virtio devices) the target guest OS can support, with the intend to become usable with modern virtualization solution such as the Cloud Hypervisor. 

## Resources

* Domain XML format for libvirt: https://libvirt.org/formatdomain.html
* qemu:///system vs qemu:///session, a great article by Cole Robinson: https://blog.wikichoon.com/2016/01/qemusystem-vs-qemusession.html