On Wed, 20 May 2020 at 08:42, Dave Airlie <airlied@xxxxxxxxx> wrote: > > On Wed, 20 May 2020 at 02:33, Sasha Levin <sashal@xxxxxxxxxx> wrote: > > > > There is a blog post that goes into more detail about the bigger > > picture, and walks through all the required pieces to make this work. It > > is available here: > > https://devblogs.microsoft.com/directx/directx-heart-linux . The rest of > > this cover letter will focus on the Linux Kernel bits. > > > > Overview > > ======== > > > > This is the first draft of the Microsoft Virtual GPU (vGPU) driver. The > > driver exposes a paravirtualized GPU to user mode applications running > > in a virtual machine on a Windows host. This enables hardware > > acceleration in environment such as WSL (Windows Subsystem for Linux) > > where the Linux virtual machine is able to share the GPU with the > > Windows host. > > > > 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. This also enables third party APIs, such as the popular NVIDIA > > Cuda compute API, to be hardware accelerated within a WSL environment. > > > > Only the rendering/compute aspect of the GPU are projected to the > > virtual machine, no display functionality is exposed. Further, at this > > time there are no presentation integration. So although the D3D12 API > > can be use to render graphics offscreen, there is no path (yet) for > > pixel to flow from the Linux environment back onto the Windows host > > desktop. This GPU stack is effectively side-by-side with the native > > Linux graphics stack. > > Okay I've had some caffiene and absorbed some more of this. > > This is a driver that connects a binary blob interface in the Windows > kernel drivers to a binary blob that you run inside a Linux guest. > It's a binary transport between two binary pieces. Personally this > holds little of interest to me, I can see why it might be nice to have > this upstream, but I don't forsee any other Linux distributor ever > enabling it or having to ship it, it's purely a WSL2 pipe. I'm not > saying I'd be happy to see this in the tree, since I don't see the > value of maintaining it upstream, but it probably should just exists > in a drivers/hyperv type area. > > Having said that, I hit one stumbling block: > "Further, at this time there are no presentation integration. " > > If we upstream this driver as-is into some hyperv specific place, and > you decide to add presentation integration this is more than likely > going to mean you will want to interact with dma-bufs and dma-fences. > If the driver is hidden away in a hyperv place it's likely we won't > even notice that feature landing until it's too late. > > I would like to see a coherent plan for presentation support (not > code, just an architectural diagram), because I think when you > contemplate how that works it will change the picture of how this > driver looks and intergrates into the rest of the Linux graphics > ecosystem. > > As-is I'd rather this didn't land under my purview, since I don't see > the value this adds to the Linux ecosystem at all, and I think it's > important when putting a burden on upstream that you provide some > value. I also have another concern from a legal standpoint I'd rather not review the ioctl part of this. I'd probably request under DRI developers abstain as well. This is a Windows kernel API being smashed into a Linux driver. I don't want to be tainted by knowledge of an API that I've no idea of the legal status of derived works. (it this all covered patent wise under OIN?) I don't want to ever be accused of designing a Linux kernel API with illgotten D3DKMT knowledge, I feel tainting myself with knowledge of a properietary API might cause derived work issues. Dave.
