On 2023/08/01 10:17, Gurchetan Singh wrote:
This adds basic documentation for virtio-gpu.Suggested-by: Akihiko Odaki <akihiko.od...@daynix.com> Signed-off-by: Gurchetan Singh <gurchetansi...@chromium.org> --- v2: - Incorporated suggestions by Akihiko Odaki - Listed the currently supported capset_names (Bernard) docs/system/device-emulation.rst | 1 + docs/system/devices/virtio-gpu.rst | 98 ++++++++++++++++++++++++++++++ 2 files changed, 99 insertions(+) create mode 100644 docs/system/devices/virtio-gpu.rst diff --git a/docs/system/device-emulation.rst b/docs/system/device-emulation.rst index 4491c4cbf7..1167f3a9f2 100644 --- a/docs/system/device-emulation.rst +++ b/docs/system/device-emulation.rst @@ -91,6 +91,7 @@ Emulated Devices devices/nvme.rst devices/usb.rst devices/vhost-user.rst + devices/virtio-gpu.rst devices/virtio-pmem.rst devices/vhost-user-rng.rst devices/canokey.rst diff --git a/docs/system/devices/virtio-gpu.rst b/docs/system/devices/virtio-gpu.rst new file mode 100644 index 0000000000..f359584033 --- /dev/null +++ b/docs/system/devices/virtio-gpu.rst @@ -0,0 +1,98 @@ +.. + SPDX-License-Identifier: GPL-2.0 + +virtio-gpu +========== + +This document explains the setup and usage of the virtio-gpu device. +The virtio-gpu device paravirtualizes the GPU and display controller. + +Linux kernel support +-------------------- + +virtio-gpu requires a guest Linux kernel built with the +``CONFIG_DRM_VIRTIO_GPU`` option. + +QEMU virtio-gpu variants +------------------------ + +QEMU provides a 2D virtio-gpu backend, and two accelerated backends: +virglrenderer ('gl' device label) and rutabaga_gfx ('rutabaga' device +label). There is a vhost-user backend that runs the graphics stack in +a separate process for improved isolation. + +Theses backends can be further classified into VGA and non-VGA variants.
It's a bit unsound wording. virglrenderer and rutabaga_gfx are certainly backends, but "VGA" is not; it describes an interface exposed to the guest
+The VGA ones are prefixed with virtio-vga or vhost-user-vga while the +non-VGA ones are prefixed with virtio-gpu or vhost-user-gpu. + +The VGA ones always use PCI interface, but for the non-VGA ones, you can +further pick simple MMIO or PCI. For MMIO, you can suffix the device +name with -device though vhost-user-gpu apparently does not support
You don't need the word "apparently" in the documentation.
+MMIO. For PCI, you can suffix it with -pci. Without these suffixes, the +platform default will be chosen. The syntax of available combinations
Duplicate whitespaces between "of" and "available".
+is listed below. + + * ``virtio-vga[-BACKEND]`` + * ``virtio-gpu[-BACKEND][-INTERFACE]`` + * ``vhost-user-vga`` + * ``vhost-user-pci``
Probably this list should come first.
+ +This document uses the PCI variant in examples. + +virtio-gpu 2d +------------- + +The default 2D backend only performs 2D operations. The guest needs to +employ a software renderer for 3D graphics. + +Typically, the software renderer is provided by `Mesa`_ or `SwiftShader`_. +Mesa's implementations (LLVMpipe, Lavapipe and virgl below) work out of box +on typical modern Linux distributions. + +.. parsed-literal:: + -device virtio-gpu-pci + +.. _Mesa: https://www.mesa3d.org/ +.. _SwiftShader: https://github.com/google/swiftshader + +virtio-gpu virglrenderer +------------------------ + +When using virgl accelerated graphics mode, OpenGL API calls are translated +into an intermediate representation (see `Gallium3D`_). The intermediate
Add "on the guest" to the first sentence for clarification.
+representation is communicated to the host and the `virglrenderer`_ library +on the host translates the intermediate representation back to OpenGL API +calls. + +.. parsed-literal:: + -device virtio-gpu-gl-pci + +.. _Gallium3D: https://www.freedesktop.org/wiki/Software/gallium/ +.. _virglrenderer: https://gitlab.freedesktop.org/virgl/virglrenderer/ + +virtio-gpu rutabaga +------------------- + +virtio-gpu can also leverage `rutabaga_gfx`_ to provide `gfxstream`_ rendering +and `Wayland display passthrough`_. With the gfxstream rendering mode, GLES +and Vulkan calls are forwarded directly to the host with minimal modification.
Nitpick: remove "directly". We already say "with minimal modification".
+ +The crosvm book provides directions on how to build a `gfxstream-enabled +rutabaga`_ and launch a `guest Wayland compositor`_.
It should be clarified it's not a conventional compositor but it's a proxy.
+ +This device does require host blob support (``hostmem`` field below), but not +all capsets (``capset_names`` below) have to enabled when starting the device. + +The currently supported ``capset_names`` are ``gfxstream-vulkan`` and +``cross-domain`` on Linux guests. For Android guests, ``gfxstream-gles`` is +also supported. + +.. parsed-literal:: + -device virtio-gpu-rutabaga-pci,capset_names=gfxstream-vulkan:cross-domain,\\ + hostmem=8G,wayland_socket_path="$XDG_RUNTIME_DIR/$WAYLAND_DISPLAY" + +.. _rutabaga_gfx: https://github.com/google/crosvm/blob/main/rutabaga_gfx/ffi/src/include/rutabaga_gfx_ffi.h +.. _gfxstream: https://android.googlesource.com/platform/hardware/google/gfxstream/ +.. _Wayland display passthrough: https://www.youtube.com/watch?v=OZJiHMtIQ2M +.. _gfxstream-enabled rutabaga: https://crosvm.dev/book/appendix/rutabaga_gfx.html +.. _guest Wayland compositor: https://crosvm.dev/book/devices/wayland.html
