ZINK support to use libvulkan on Virtio-GPU

[Mike Blumenkrantz]

Hi,

If you aren't hitting the kopper init paths (e.g., kopper_init_screen),
you're doing something wrong.

I'm not sure exactly what's going on there with gfxstream, but for gbm+zink
you should be getting a backtrace like this on init:

#0 kopper_init_screen (screen=0x25e010, driver_name_is_inferred=false) at
../src/gallium/frontends/dri/kopper.c:117
#1 0x00007ffff486dc77 in driCreateNewScreen3 (scrn=0, fd=7,
loader_extensions=0x7ffff7e6c2e0 <gbm_dri_screen_extensions>,
driver_extensions=0x7ffff72ff760 <galliumvk_driver_extensions>,
driver_configs=0x25df98, driver_name_is_inferred=false, data=0x25de50) at
../src/gallium/frontends/dri/dri_util.c:140
#2 0x00007ffff7e5cdf8 in dri_screen_create_for_driver (dri=0x25de50,
driver_name=0x25dc10 "zink", driver_name_is_inferred=false) at
../src/gbm/backends/dri/gbm_dri.c:300
#3 0x00007ffff7e5cf0d in dri_screen_create (dri=0x25de50,
driver_name_is_inferred=false) at ../src/gbm/backends/dri/gbm_dri.c:337
#4 0x00007ffff7e5f0f1 in dri_device_create (fd=7, gbm_backend_version=1) at
../src/gbm/backends/dri/gbm_dri.c:1268
#5 0x00007ffff7e5b76f in backend_create_device (bd=0x7ffff7e6b310
<builtin_backends>, fd=7) at ../src/gbm/main/backend.c:105
#6 0x00007ffff7e5b8d2 in find_backend (name=0x0, fd=7) at
../src/gbm/main/backend.c:163
#7 0x00007ffff7e5ba72 in _gbm_create_device (fd=7) at
../src/gbm/main/backend.c:229
#8 0x00007ffff7e5bbd2 in gbm_create_device (fd=7) at
../src/gbm/main/gbm.c:138


Regards,
Mike

On Mon, Jul 22, 2024 at 10:40 AM Lei Zhou <lei.zhou at linaro.org> wrote:

> Dear mesa/experts,
>
> Need your support to help us better understand how we can go about this
> behavior.
>
> Here is what we have:
>      1.    We are running QEMU based Debian guest with -device
> virtio-gpu-rutabaga,gfxstream-vulkan=on,cross-domain=on.   Expect to run
> vulkan application eg.vkcube-wayland from guest via wayland proxy over
> gfxstream and wayland protocol.   Please check this link (
> https://www.qemu.org/docs/master/system/devices/virtio-gpu.html) for what
> is rutabaga/gfxstream GPU mode.     In theory,  it should be sufficient to
> render vkcube graphics over vulkan/gfxstream/virtio-gpu via host wayland
> compositor with a physical GPU driver.
>   2.  On guest side mesa,  we compile with these options
>       -Dgallium-drivers=radeonsi,virgl,zink -Dvulkan-drivers=virtio,amd.
> 3.  When running $vkcube-wayland with wayland proxy,
> gbm_create_device(...) will be invoked to acquire drm device resource,
> which will invoke driCreateNewScreen2 -> dri2_init_screen() etc.
>
>     *within mesa/src/gallium/frontends/dri/dri2.c,  what was the
> intention to indicate that "no zink" will be used?*
> ===========================================
> #ifdef HAVE_LIBDRM
> if (pipe_loader_drm_probe_fd(&screen->dev, screen->fd, *false*)) <<=== *ZINK
> usage*
>       pscreen = pipe_loader_create_screen(screen->dev,
> driver_name_is_inferred);
> #endif
> =============================================
>
> 4.  In current behavior, virtio_gpu_driver_descriptor will be discovered
> and used.  Which will depend on "-device virtio-gpu-gl-pci" the capsets
> of virgl and virgl2, which is not what we are using.
>
>
> Any clarification will be highly appreciated!
>
> Lei Zhou
>
>
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