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title: Virtual Function I/O Mediated devices (vfio-mdev) title: Virtual Function I/O Mediated devices (vfio-mdev)
description: Create and Configure Virtual Function I/O Mediated devices (vfio-mdev) description: Create and Configure Virtual Function I/O Mediated devices (vfio-mdev)
published: true published: true
date: 2023-01-29T20:12:01.722Z date: 2023-05-14T20:10:36.548Z
tags: tags:
editor: markdown editor: markdown
dateCreated: 2022-07-21T21:10:41.046Z dateCreated: 2022-07-21T21:10:41.046Z
--- ---
# Configure Virtual Function I/O Mediated devices # Configure *vfio-mdev*
> These instructions only cover Intel GPUs that are compatible with vfio-mdev (5th to 10th generation). Since generation 11th, vfio-mdev has been superseded by SR-IOV. > These instructions only cover **Intel GPUs** that are compatible with *vfio-mdev* (5th to 10th generation). Since generation 11th, *vfio-mdev* has been superseded by *SR-IOV*.
{.is-warning} {.is-warning}
GPUs compatible with [Virtual Function I/O Mediated devices](https://www.kernel.org/doc/html/latest/driver-api/vfio-mediated-device.html) (vfio-mdev) can be split into multiple virtual GPUs (vGPUs). GPUs compatible with [Virtual Function I/O Mediated devices](https://www.kernel.org/doc/html/latest/driver-api/vfio-mediated-device.html) (vfio-mdev) can be split into multiple virtual GPUs (vGPUs).
In turned, these vGPUs can then be assigned to virtual machines or containers. Then, these vGPUs can be assigned to virtual machines or containers.
Contrary to paravirtualized GPUs (e.g. virtio-gpu), virtual GPUs do not need specialized drivers. Contrary to paravirtualized GPUs (e.g. *virtio-gpu*), vGPUs can use the same driver as their parent GPU (e.g. a guest compatible with an Intel GPUs will be able to leverage an Intel-based vGPUs)
*How to do so?*
## Preparation ## Preparation
* Make sure the GRUB has been updated after [the first boot](https://wiki.phyllo.me/getstarted/disk#update-grub-and-reboot) * Make sure the GRUB has been updated after [the first boot](https://wiki.phyllo.me/getstarted/disk#update-grub-and-reboot)
### Modify the system allocated to the GPU in the BIOS/UEFI ## Procedure
> Some computers allow you to modify the system memory allocated or shared with the integrated GPU, which may allow you to create more vGPUs. ### Create a virtual GPU
{.is-info}
List available GPUs using the `mdevctl` software:
* Before the host operating system boots up, you need to enter the BIOS/UEFI and to look for a setting called *GPU aperture size*, or *GPU shared memory*.
* Use the highest possible value.
> System memory will be reserved for the GPU, so make sure you have enough system memory to accomodate both the GPU and your operating system.
{.is-info}
## Create a virtual GPU
Upon reboot, you should then be able to list available GPUs using the `mdevctl` command.
* List available virtual GPUs:
``` ```
mdevctl types mdevctl types
@ -69,7 +53,7 @@ mdevctl types
Description: low_gm_size: 64MB, high_gm_size: 384MB, fence: 4, resolution: 1024x768, weight: 2 Description: low_gm_size: 64MB, high_gm_size: 384MB, fence: 4, resolution: 1024x768, weight: 2
``` ```
> Increasing the system memory allocated to the GPU (GPU aperture size), as shown in the previous section, may increase the number and kind of available instances. > Increasing the memory allocated to the GPU in the BIOS/EFI may increase the number and kind of available instances.
{.is-info} {.is-info}
@ -91,13 +75,13 @@ uuidgen
sudo mdevctl start -u 7686131b-b229-4768-a02c-35d1dbed7c66 -p 0000:00:02.0 --type i915-GVTg_V5_4 sudo mdevctl start -u 7686131b-b229-4768-a02c-35d1dbed7c66 -p 0000:00:02.0 --type i915-GVTg_V5_4
``` ```
* Define, or make this vGPU permanent. * Define, or make this vGPU permanent:
``` ```
sudo mdevctl define -u 7686131b-b229-4768-a02c-35d1dbed7c66 sudo mdevctl define -u 7686131b-b229-4768-a02c-35d1dbed7c66
``` ```
* Set the vGPU to auto-start after the host boots up, so that it is available to guest virtual machines without further action * Set the vGPU to auto-start after the host boots up:
``` ```
sudo mdevctl modify -u 7686131b-b229-4768-a02c-35d1dbed7c66 --auto sudo mdevctl modify -u 7686131b-b229-4768-a02c-35d1dbed7c66 --auto
@ -113,16 +97,14 @@ mdevctl list -d
7686131b-b229-4768-a02c-35d1dbed7c66 0000:00:02.0 i915-GVTg_V5_4 auto (active) 7686131b-b229-4768-a02c-35d1dbed7c66 0000:00:02.0 i915-GVTg_V5_4 auto (active)
``` ```
Great you have ### Assign a vGPU to a virtual machine
## Assign a virtual GPU to a virtual machine * Add that segment to a virtual machine's definition. Make sure the provided `uuid` matches the previously generated UUID.
* Add that segment to a virtual machine's definition. Make sure the provided ```uuid``` matches the previously generated UUID.
``` ```
<domain> <domain type="kvm">
[...] [...]
<device> <device>
[...] [...]
<hostdev mode="subsystem" type="mdev" managed="no" model="vfio-pci" display="on" ramfb="on"> <hostdev mode="subsystem" type="mdev" managed="no" model="vfio-pci" display="on" ramfb="on">
<source> <source>
@ -131,41 +113,55 @@ Great you have
<address type="pci" domain="0x0000" bus="0x09" slot="0x00" function="0x0"/> <address type="pci" domain="0x0000" bus="0x09" slot="0x00" function="0x0"/>
</hostdev> </hostdev>
[...] [...]
</device> </device>
[...] [...]
</domain> </domain>
``` ```
> Notice that the RAMFB is set to on, which activates Drect Memory Access Buffers (DMA-BUFs), making available the output of a virtual monitor before the guest operating system takes over > Notice that the RAMFB is set to on, which activates Drect Memory Access Buffers (DMA-BUFs), making the output of a virtual monitor available before the guest operating system takes over.
{.is-info} {.is-info}
## Configure Spice / SDL ## Remove any video device or display devices
*To-do*
## Remove any video device
* Remove any video device such as `virtio-gpu` and set the last one to the `none`. * Remove any video device such as `virtio-gpu` and set the last one to the `none`.
``` ```
<domain> <domain type="kvm">
[...] [...]
<device> <device>
[...] [...]
<video> <video>
<model type="none"/> <model type="none"/>
</video> </video>
[...] [...]
</device> </device>
[...] [...]
</domain> </domain>
``` ```
* Then starts the domain * Then starts the domain
## Configure Spice / SDL
*To-do*
## Troubleshooting
### No or low number of available instances
Increasing the memory allocated to the GPU (a.k.a. the GPU aperture size) may increase the number of available instances.
Some computers allow you to modify the memory allocated or shared with the integrated GPU, which may allow you to create more vGPUs.
* Before the host operating system boots up, enter the BIOS/UEFI and look for a setting called *GPU aperture size*, or *GPU shared memory*.
* Use the highest possible value.
> The memory will be reserved to the GPU, so make sure you have enough leftover memory to accomodate both the GPU and your operating system.
{.is-info}
## Resources ## Resources
* Official page for vfio-mdev: https://www.kernel.org/doc/html/latest/driver-api/vfio-mediated-device.html * Official page for vfio-mdev: https://www.kernel.org/doc/html/latest/driver-api/vfio-mediated-device.html
* Archlinux's *must read entry* on Intel GVT-g: https://wiki.archlinux.org/title/Intel_GVT-g * Archlinux's *must-read entry* on Intel GVT-g: https://wiki.archlinux.org/title/Intel_GVT-g
* DMA-BUF Linux documentation: https://www.kernel.org/doc/html/latest/driver-api/dma-buf.html * DMA-BUF Linux documentation: https://www.kernel.org/doc/html/latest/driver-api/dma-buf.html