According to the comment by christoph-heiss, this is just a paravirtualisation technique and will appear like a normal Limux GPU driver to applications running on WSL, rather than a special DirectX for Linux API that won't work on Linux itself.
From the email introducing the set of patches:
> The projection is accomplished by exposing the WDDM (Windows Display Driver Model) interface as a set of IOCTL. This allows APIs and user mode driver written against the WDDM GPU abstraction on Windows to be ported to run within a Linux environment. This enables the port of the D3D12 and DirectML APIs as well as their associated user mode driver to Linux.
The fact that they went through the effort of porting Mesa to get OpenGL and Open CL support, and are working on Vulkan support.
Their porting Mesa to use a proprietary library that interacts with the wsl only kernel interface isn't that same as behaving like a standard Linux gpu
And part of the discussion on the mailing list is how to integrate this with DRI/DRM and dma-buf so it can be used by more Linux clients with less work (although still non zero like you'd have on a DRI scheme as well).
Are we reading the same blog post?[1]
[1]: https://devblogs.microsoft.com/directx/wp-content/uploads/si...