Building new WSL2 Linux Kernel 6.6 disables /dev/dri (and VA-API)

[sikhness]

Windows Version

Microsoft Windows [Version 10.0.20348.2582] (Windows Server 2022)

WSL Version

2.2.4.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

6.6.36.3-microsoft-standard-WSL2

Distro Version

Ubuntu 24.04

Other Software

No response

Repro Steps

1. Build the new WSL2 Linux 6.6.36.3 kernel release
2. Spin up a Ubuntu 24.04 (or even Ubuntu 22.04) WSL2 instance
3. Observe that /dev/dri is not there

Expected Behavior

/dev/dri should be present just like before using the older kernel

Actual Behavior

/dev/dri is missing and this makes VA-API impossible.

Workaround

I think the issue seems to be around the way the kernel config is set up. After much debugging, I found that /dev/dri is mapped using VGEM as described in this commit. I then noticed that in the config for the kernel, CONFIG_DRM_VGEM=m instead of CONFIG_DRM_VGEM=y like in the older WSL2 kernels. After changing the m to y for CONFIG_DRM_VGEM and rebuilding the WSL2 kernel, /dev/dri seems to show up again.

This should probably be fixed directly in the config.

Diagnostic Logs

No response

[github-actions]

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View similar issues

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Closed similar issues:

• No /dev/dri on WSL2? (#5822), similarity score: 0.74

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[sikhness]

/feature

I'm tagging this as a feature request since I have provided the solution in the workaround. No logs are really needed as this one involves building the kernel and following the steps to reproduce the issue.

[github-actions]

Diagnostic information

Found '/feature', adding tag 'feature'

[zcobol]

From https://github.com/microsoft/WSL2-Linux-Kernel/releases

We are very excited kernel module support is now available in WSL2! With this latest kernel update, a large set of loadable modules has been introduced, accompanied by an overall config file update. However, please be aware that when using a custom kernel, the default module support is disabled for now. If you’re using a custom kernel, we recommend you edit your kernel config file to build-in all of the modules that you need.

[sikhness]

Thanks @zcobol, I did read that as part of the release notes, but since this is to be the new LTS kernel and the default one at some point soon when you update WSL, I'd imagine that feature (CONFIG_DRM_VGEM) should be enabled by default. Perhaps it is planned to be done, but I just wanted to open an issue regarding that in case it was not (especially since VA-API is a supported and default feature set for WSL).

[benhillis]

The kernel module is included, can you simply load the module (sudo modprobe vgem)?

[sikhness]

@benhillis, I haven't tried loading it explicitly, but I raised this issue hoping that in the WSL2 kernel code, perhaps it's a good idea to have it enabled by default so that manual commands don't need to be run each time WSL2 is started to load the VGEM module. It should in theory work out-of-the-box as it does in the older 5.15 kernel.

[Starstrike]

Just updated WSL to 2.3.13 and also noticed that /dev/dri was missing. This is required for Emby Media Server to run. Using the sudo modprobe vgem worked, but if this is something that has to be done every time the server restarts, then it really should be enabled by default.