Hi Steve, thank you for the fast reply.
Am 20.05.20 um 09:42 schrieb Steve Pronovost: >> Echoing what others said, you're not making a DRM driver. The driver should >> live outside of the DRM code. > > Agreed, please see my earlier reply. We'll be moving the driver to > drivers/hyperv node or something similar. Apology for the confusion here. > >> I have one question about the driver API: on Windows, DirectX versions are >> loosly tied to Windows releases. So I guess you can change the kernel >> interface among DirectX versions? >> If so, how would this work on Linux in the long term? If there ever is a >> DirectX 13 or 14 with incompatible kernel interfaces, how would you plan to >> update the Linux driver? > > You should think of the communication over the VM Bus for the vGPU projection > as a strongly versioned interface. We will be keeping compatibility with > older version of that interface as it evolves over time so we can continue to > run older guest (we already do). This protocol isn't actually tied to the DX > API. It is a generic abstraction for the GPU that can be used for any APIs > (for example the NVIDIA CUDA driver that we announced is going over the same > protocol to access the GPU). > > New version of user mode DX can either take advantage or sometime require new > services from this kernel abstraction. This mean that pulling a new version > of user mode DX can mean having to also pull a new version of this vGPU > kernel driver. For WSL, these essentially ships together. The kernel driver > ships as part of our WSL2 Linux Kernel integration. User mode DX bits ships > with Windows. Just a friendly advise: maintaining a proprietary component within a Linux environment is tough. You will need a good plan for long-term interface stability and compatibility with the other components. Best regards Thomas > > -----Original Message----- > From: Thomas Zimmermann <tzimmerm...@suse.de> > Sent: Wednesday, May 20, 2020 12:11 AM > To: Sasha Levin <sas...@kernel.org>; alexander.deuc...@amd.com; > ch...@chris-wilson.co.uk; ville.syrj...@linux.intel.com; > hawking.zh...@amd.com; tvrtko.ursu...@intel.com > Cc: linux-ker...@vger.kernel.org; linux-hyp...@vger.kernel.org; KY Srinivasan > <k...@microsoft.com>; Haiyang Zhang <haiya...@microsoft.com>; Stephen > Hemminger <sthem...@microsoft.com>; wei....@kernel.org; Steve Pronovost > <spron...@microsoft.com>; Iouri Tarassov <iou...@microsoft.com>; > dri-devel@lists.freedesktop.org; linux-fb...@vger.kernel.org; > gre...@linuxfoundation.org > Subject: [EXTERNAL] Re: [RFC PATCH 0/4] DirectX on Linux > > Hi > > Am 19.05.20 um 18:32 schrieb Sasha Levin: >> 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. > > That's quite a surprise. Thanks for your efforts to contribute. > >> >> 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. >> >> The driver creates the /dev/dxg device, which can be opened by user >> mode application and handles their ioctls. The IOCTL interface to the >> driver is defined in dxgkmthk.h (Dxgkrnl Graphics Port Driver ioctl >> definitions). The interface matches the D3DKMT interface on Windows. >> Ioctls are implemented in ioctl.c. > > Echoing what others said, you're not making a DRM driver. The driver should > live outside of the DRM code. > > I have one question about the driver API: on Windows, DirectX versions are > loosly tied to Windows releases. So I guess you can change the kernel > interface among DirectX versions? > > If so, how would this work on Linux in the long term? If there ever is a > DirectX 13 or 14 with incompatible kernel interfaces, how would you plan to > update the Linux driver? > > Best regards > Thomas > >> >> When a VM starts, hyper-v on the host adds virtual GPU devices to the >> VM via the hyper-v driver. The host offers several VM bus channels to >> the >> VM: the global channel and one channel per virtual GPU, assigned to >> the VM. >> >> The driver registers with the hyper-v driver (hv_driver) for the >> arrival of VM bus channels. dxg_probe_device recognizes the vGPU >> channels and creates the corresponding objects (dxgadapter for vGPUs >> and dxgglobal for the global channel). >> >> The driver uses the hyper-V VM bus interface to communicate with the >> host. dxgvmbus.c implements the communication interface. >> >> The global channel has 8GB of IO space assigned by the host. This >> space is managed by the host and used to give the guest direct CPU >> access to some allocations. Video memory is allocated on the host >> except in the case of existing_sysmem allocations. The Windows host >> allocates memory for the GPU on behalf of the guest. The Linux guest >> can access that memory by mapping GPU virtual address to allocations >> and then referencing those GPU virtual address from within GPU command >> buffers submitted to the GPU. For allocations which require CPU >> access, the allocation is mapped by the host into a location in the >> 8GB of IO space reserved in the guest for that purpose. The Windows >> host uses the nested CPU page table to ensure that this guest IO space >> always map to the correct location for the allocation as it may >> migrate between dedicated GPU memory (e.g. VRAM, firmware reserved >> DDR) and shared system memory (regular DDR) over its lifetime. The >> Linux guest maps a user mode CPU virtual address to an allocation IO >> space range for direct access by user mode APIs and drivers. >> >> >> >> Implementation of LX_DXLOCK2 ioctl >> ================================== >> >> We would appreciate your feedback on the implementation of the >> LX_DXLOCK2 ioctl. >> >> This ioctl is used to get a CPU address to an allocation, which is >> resident in video/system memory on the host. The way it works: >> >> 1. The driver sends the Lock message to the host >> >> 2. The host allocates space in the VM IO space and maps it to the >> allocation memory >> >> 3. The host returns the address in IO space for the mapped allocation >> >> 4. The driver (in dxg_map_iospace) allocates a user mode virtual >> address range using vm_mmap and maps it to the IO space using >> io_remap_ofn_range) >> >> 5. The VA is returned to the application >> >> >> >> Internal objects >> ================ >> >> The following objects are created by the driver (defined in dxgkrnl.h): >> >> - dxgadapter - represents a virtual GPU >> >> - dxgprocess - tracks per process state (handle table of created >> objects, list of objects, etc.) >> >> - dxgdevice - a container for other objects (contexts, paging queues, >> allocations, GPU synchronization objects) >> >> - dxgcontext - represents thread of GPU execution for packet >> scheduling. >> >> - dxghwqueue - represents thread of GPU execution of hardware >> scheduling >> >> - dxgallocation - represents a GPU accessible allocation >> >> - dxgsyncobject - represents a GPU synchronization object >> >> - dxgresource - collection of dxgalloction objects >> >> - dxgsharedresource, dxgsharedsyncobj - helper objects to share objects >> between different dxgdevice objects, which can belong to different >> processes >> >> >> >> Object handles >> ============== >> >> All GPU objects, created by the driver, are accessible by a handle >> (d3dkmt_handle). Each process has its own handle table, which is >> implemented in hmgr.c. For each API visible object, created by the >> driver, there is an object, created on the host. For example, the is a >> dxgprocess object on the host for each dxgprocess object in the VM, etc. >> The object handles have the same value in the host and the VM, which >> is done to avoid translation from the guest handles to the host handles. >> >> >> >> Signaling CPU events by the host >> ================================ >> >> The WDDM interface provides a way to signal CPU event objects when >> execution of a context reached certain point. The way it is implemented: >> >> - application sends an event_fd via ioctl to the driver >> >> - eventfd_ctx_get is used to get a pointer to the file object >> (eventfd_ctx) >> >> - the pointer to sent the host via a VM bus message >> >> - when GPU execution reaches a certain point, the host sends a message >> to the VM with the event pointer >> >> - signal_guest_event() handles the messages and eventually >> eventfd_signal() is called. >> >> >> Sasha Levin (4): >> gpu: dxgkrnl: core code >> gpu: dxgkrnl: hook up dxgkrnl >> Drivers: hv: vmbus: hook up dxgkrnl >> gpu: dxgkrnl: create a MAINTAINERS entry >> >> MAINTAINERS | 7 + >> drivers/gpu/Makefile | 2 +- >> drivers/gpu/dxgkrnl/Kconfig | 10 + >> drivers/gpu/dxgkrnl/Makefile | 12 + >> drivers/gpu/dxgkrnl/d3dkmthk.h | 1635 +++++++++ >> drivers/gpu/dxgkrnl/dxgadapter.c | 1399 ++++++++ >> drivers/gpu/dxgkrnl/dxgkrnl.h | 913 ++++++ >> drivers/gpu/dxgkrnl/dxgmodule.c | 692 ++++ >> drivers/gpu/dxgkrnl/dxgprocess.c | 355 ++ >> drivers/gpu/dxgkrnl/dxgvmbus.c | 2955 +++++++++++++++++ >> drivers/gpu/dxgkrnl/dxgvmbus.h | 859 +++++ >> drivers/gpu/dxgkrnl/hmgr.c | 593 ++++ >> drivers/gpu/dxgkrnl/hmgr.h | 107 + >> drivers/gpu/dxgkrnl/ioctl.c | 5269 ++++++++++++++++++++++++++++++ >> drivers/gpu/dxgkrnl/misc.c | 280 ++ >> drivers/gpu/dxgkrnl/misc.h | 288 ++ >> drivers/video/Kconfig | 2 + >> include/linux/hyperv.h | 16 + >> 18 files changed, 15393 insertions(+), 1 deletion(-) create mode >> 100644 drivers/gpu/dxgkrnl/Kconfig create mode 100644 >> drivers/gpu/dxgkrnl/Makefile create mode 100644 >> drivers/gpu/dxgkrnl/d3dkmthk.h create mode 100644 >> drivers/gpu/dxgkrnl/dxgadapter.c create mode 100644 >> drivers/gpu/dxgkrnl/dxgkrnl.h create mode 100644 >> drivers/gpu/dxgkrnl/dxgmodule.c create mode 100644 >> drivers/gpu/dxgkrnl/dxgprocess.c create mode 100644 >> drivers/gpu/dxgkrnl/dxgvmbus.c create mode 100644 >> drivers/gpu/dxgkrnl/dxgvmbus.h create mode 100644 >> drivers/gpu/dxgkrnl/hmgr.c create mode 100644 >> drivers/gpu/dxgkrnl/hmgr.h create mode 100644 >> drivers/gpu/dxgkrnl/ioctl.c create mode 100644 >> drivers/gpu/dxgkrnl/misc.c create mode 100644 >> drivers/gpu/dxgkrnl/misc.h >> > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Felix Imendörffer > -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
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