Re: [PATCH 0/3] virtio-gpu: Enable virglrenderer backend for rutabaga

["Alex Bennée" <alex.bennee@linaro.org>]

Weifeng Liu <weifeng.liu.z@gmail.com> writes:

> Greetings,
>
> I'd like to introduce you my attempt to enable virglrenderer backend for
> rutabaga empowered virtio-gpu device.  I am aware that there have been
> effort in supporting venus in virtio-gpu-virgl.c [1], but there is no
> reason to prevent us from leveraging the virglrenderer component in
> rutabaga_gfx, especially it being not very hard to add this
> functionality.
>
> Generally, the gap is the polling capability, i.e., virglrenderer
> requires the main thread (namely the GPU command handling thread) to
> poll virglrenderer at proper moments, which is not yet supported in
> virtio-gpu-rutabaga device. This patch set try to add this so that
> virglrenderer backend (including virgl and venus) can work as expected.
>
> Slight change to rutabaga_gfx_ffi is also a requirement, which is
> included in [2].
>
> Further effort is required to tune the performance, since copying is
> present before the rendered images get displayed. But I still think this
> patch set could be a good starting point for the pending work.
>
> For those interested in setting up environment and playing around with
> this patch set, here is guideline in brief:
>
> 1. Clone the master/main branch of virglrenderer, compile and install it.
>
> 	git clone https://gitlab.freedesktop.org/virgl/virglrenderer
> 	cd virglrenderer
> 	meson setup builddir \
> 	  --prefix=$INSTALL_DIR/virglrenderer \
> 	  -Dvenus=true
> 	ninja -C builddir install
>
> 2. Clone the patched CrosVM, build and install rutabaga_gfx_ffi.
>
> 	git clone -b rutabaga_ffi_virgl https://github.com/phreer/crosvm.git
> 	cd crosvm/rutabaga_gfx/ffi
> 	export PKG_CONFIG_PATH=$INSTALL_DIR/virglrenderer/lib64/pkgconfig/
> 	meson setup builddir/ \
> 	  --prefix $HOME/install/rutabaga_gfx/rutabaga_gfx_ffi/ \
> 	  -Dvirglrenderer=true
> 	ninja -C builddir install

Is there a PR going in for this? The moving parts for rutabaga are
complex enough I think we need support upstream before merging this.

Is this branch where I should be getting the poll helpers from?

  cc -m64 @qemu-system-arm.rsp
  /usr/bin/ld: libcommon.fa.p/hw_display_virtio-gpu-rutabaga.c.o: in function `virtio_gpu_fence_poll':
  /home/alex/lsrc/qemu.git/builds/vulkan/../../hw/display/virtio-gpu-rutabaga.c:909: undefined reference to `rutabaga_poll'
  /usr/bin/ld: libcommon.fa.p/hw_display_virtio-gpu-rutabaga.c.o: in function `virtio_gpu_rutabaga_init':
  /home/alex/lsrc/qemu.git/builds/vulkan/../../hw/display/virtio-gpu-rutabaga.c:1122: undefined reference to `rutabaga_poll_descriptor'
  collect2: error: ld returned 1 exit status
  ninja: build stopped: subcommand failed.


> 3. Applied this patch set to QEMU, build and install it:
>
> 	cd qemu	
> 	# Apply this patch set atop main branch ...
> 	mkdir builddir; cd builddir
> 	../configure --prefix=$INSTALL_DIR/qemu \
> 	  --target-list=x86_64-softmmu \
> 	  --disable-virglrenderer \
> 	  --enable-rutabaga_gfx
> 	ninja -C builddir install
>
> 4. If you are lucky and everything goes fine, you are prepared to launch
>    VM with virglrenderer backed virtio-gpu-rutabaga device:
>
> 	export LD_LIBRARY_PATH=$INSTALL_DIR/virglrenderer/lib64/:$LD_LIBRARY_PATH
> 	export LD_LIBRARY_PATH=$INSTALL_DIR/rutabaga_gfx_ffi/lib64/:$LD_LIBRARY_PATH
> 	$INSTALL_DIR/qemu/bin/qemu-system-x86_64
> 	$QEMU -d guest_errors -enable-kvm -M q35 -smp 4 -m $MEM \
> 	  -object memory-backend-memfd,id=mem1,size=$MEM \
> 	  -machine memory-backend=mem1 \
> 	  -device virtio-vga-rutabaga,venus=on,virgl2=on,wsi=surfaceless,hostmem=$MEM \
>

This should go into docs/system/devices/virtio-gpu.rst with some
explanation. Is there anything we need on the guest side or does this
skip the encapsulating requirements of wayland?

> Note:
>
> - You might need this patch set [3] to avoid KVM bad address error when
>   you are running on a GPU using TTM for memory management.
>
> [1] https://lore.kernel.org/all/dba6eb97-e1d1-4694-bfb6-e72db95715dd@daynix.com/T/
> [2] https://chromium-review.googlesource.com/c/crosvm/crosvm/+/5599645/1
> [3] https://lore.kernel.org/kvm/20240229025759.1187910-1-stevensd@google.com/
>
> Weifeng Liu (3):
>   virtio-gpu: rutabaga: Properly set stride when copying resources
>   virtio-gpu: rutabaga: Poll rutabaga upon events
>   virtio-gpu: rutabaga: Add options to enable virgl and venus contexts
>
>  hw/display/virtio-gpu-rutabaga.c | 104 ++++++++++++++++++++++++++++++-
>  include/hw/virtio/virtio-gpu.h   |   1 +
>  2 files changed, 104 insertions(+), 1 deletion(-)

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro