It has been a while since the last XDC talk about the VKMS and a lot has changed. VKMS now supports multiple formats, the composition is now performed in CRTC, the performance was improved and the planes now have the ability to rotate. And there is more coming: 1D LUT, multi-planar formats, full blend mode support... So, let's explore a bit of the current status of VKMS, see the current state of its IGT test coverage, and also cover some current use cases for it. (c) X.Org Developer's Conference (XDC) 2023 October 17-19, 2023 A Coruña (Spain) https://indico.freedesktop.org/event/4/

1. Status Update of the VKMS DRM
driver
Maíra Canal and Melissa Wen
A Coruña, XDC 2023

2. Virtual Kernel Mode Setting
VKMS is a software-only model of a KMS driver
● useful for testing and for running X (or similar) on headless machines;
● aims to enable a virtual display with no need of a hardware display capability;
DRM community project. GPU-vendor agnostic.
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

3. Performance Improvement
Performance has been a historical problem for VKMS
We were able to improve the performance (~30%)
● All planes are blended at once.
● The blend calculus is done as per line instead of per pixel.
Memory consumption also improved: from width * height to 2 * width
● We don't need the whole image at once.
No more IGT timeouts :)
Thanks Igor Torrente and Pekka Paalanen!
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

4. The composition was executed on top of the primary plane.
● The primary plane needed to be enabled, visible and have the same size and
position as the CRTC.
Now, the composition is performed on top of a black background with the size of
the CRTC.
● The primary plane doesn't have to be visible, or even enabled.
● It can be positioned.
Full alpha-blending on all planes.
More IGT tests are passing!
Composition
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

5. Support for multiple overlay planes when enable_overlay=1
● Thanks José Exposito!
VKMS used to support only ARGB8888 and XRGB8888.
● Format support was really attached to blending.
Now, VKMS has support for ARGB8888, XRGB8888, ARGB16161616, XRGB16161616,
and RGB565.
● Thanks Igor Torrente!
New features
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

6. Support for plane rotation
● rotate-0, rotate-90, rotate-180, rotate-270, reflect-x and reflect-y.
Support a 1D gamma LUT with interpolation for each color channel.
● Thanks Arthur Grillo!
More IGT tests are passing!
New features
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

7. Synchronization issues
● Deadlock between dev->event_lock and timer
● Race-condition between flushing and destroying
● Race-condition between the hrtimer and the atomic commit
Implement blend mode properties
Enable Virtual Hardware support
Support for multi-planar formats (e.g. NV12)
● Thanks Arthur Grillo!
Ongoing
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

8. Support for multiple CRTCs
● Thanks Marius Vlad, Brandon Pollack and Jim Shargo!
Planes / CRTCs / Connectors setup via ConfigFS
● Thanks Brandon Pollack and Jim Shargo!
Addition of VKMS to the DRM CI pipeline
● Thanks Helen Koike!
Extending the color management support
● Thanks Harry Wentland!
Incoming work
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

9. https://dri.freedesktop.org/docs/drm/gpu/vkms.html#todo
Unit tests for the composition procedure
Fix failing tests on IGT detected by the DRM CI
TO-DO
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

10. Testing Requirements for Userspace API
Anything that constitutes an API change should have driver-agnostic test cases
in IGT for that feature.
What if support on VKMS became a requirement for new KMS/generic APIs?
VKMS DRM/KMS API
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023

11. Getting started: https://docs.kernel.org/gpu/vkms.html
We need more reviewers!
Increase coverage of IGT tests
Do you want to contribute?
Status Update of the VKMS DRM driver
Maíra Canal and Melissa Wen, XDC 2023