Re: [PATCH v3 6/6] virtio-gpu: Support DRM native context

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

Dmitry Osipenko <dmitry.osipenko@collabora.com> writes:

> Add support for DRM native contexts to VirtIO-GPU. DRM context is enabled
> using a new virtio-gpu-gl device option "drm=on".

I feel like using "drm" is confusing in this context because drm exists
for the host and guest. What about "native-context" or even
"context=[opengl|vulkan|wayland|native]"?

The GPU command line is already getting complex so now might be the time
to rationalise it.

As an aside can mesa build the intel drivers on non-x86 systems as now I
could potentially pass my native intel context to my emulated aarch64
guests?

>
> Unlike Virgl and Venus contexts that operate on application API level,
> DRM native contexts work on a kernel UAPI level. This lower level results
> in a lightweight context implementations that yield better performance.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  docs/system/devices/virtio-gpu.rst | 11 +++++++++++
>  hw/display/virtio-gpu-gl.c         |  2 ++
>  hw/display/virtio-gpu-virgl.c      | 22 ++++++++++++++++++++++
>  hw/display/virtio-gpu.c            | 15 +++++++++++++++
>  include/hw/virtio/virtio-gpu.h     |  3 +++
>  5 files changed, 53 insertions(+)
>
> diff --git a/docs/system/devices/virtio-gpu.rst b/docs/system/devices/virtio-gpu.rst
> index b7eb0fc0e727..49a75138f7ef 100644
> --- a/docs/system/devices/virtio-gpu.rst
> +++ b/docs/system/devices/virtio-gpu.rst
> @@ -82,6 +82,17 @@ of virtio-gpu host memory window. This is typically between 256M and 8G.
>  
>  .. _venus: https://gitlab.freedesktop.org/virgl/venus-protocol/
>  
> +DRM native context is supported since release of `virglrenderer`_ v1.0.0
> +using `drm`_ protocol. ``DRM`` virtio-gpu capability set ("capset") requires
> +host blob support (``hostmem`` and ``blob`` fields) and should be enabled
> +using ``drm`` field. The ``hostmem`` field specifies the size of virtio-gpu
> +host memory window. This is typically between 256M and 8G.
> +
> +.. parsed-literal::
> +    -device virtio-gpu-gl,hostmem=8G,blob=on,drm=on
> +
> +.. _drm: https://gitlab.freedesktop.org/virgl/virglrenderer/-/tree/main/src/drm
> +
>  virtio-gpu rutabaga
>  -------------------
>  
> diff --git a/hw/display/virtio-gpu-gl.c b/hw/display/virtio-gpu-gl.c
> index 53d938f23f20..bd0c0692a5c4 100644
> --- a/hw/display/virtio-gpu-gl.c
> +++ b/hw/display/virtio-gpu-gl.c
> @@ -159,6 +159,8 @@ static Property virtio_gpu_gl_properties[] = {
>                      VIRTIO_GPU_FLAG_STATS_ENABLED, false),
>      DEFINE_PROP_BIT("venus", VirtIOGPU, parent_obj.conf.flags,
>                      VIRTIO_GPU_FLAG_VENUS_ENABLED, false),
> +    DEFINE_PROP_BIT("drm", VirtIOGPU, parent_obj.conf.flags,
> +                    VIRTIO_GPU_FLAG_DRM_ENABLED, false),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
> index 37b40e258398..89ca1878fb7c 100644
> --- a/hw/display/virtio-gpu-virgl.c
> +++ b/hw/display/virtio-gpu-virgl.c
> @@ -1232,6 +1232,19 @@ int virtio_gpu_virgl_init(VirtIOGPU *g)
>      if (virtio_gpu_venus_enabled(g->parent_obj.conf)) {
>          flags |= VIRGL_RENDERER_VENUS | VIRGL_RENDERER_RENDER_SERVER;
>      }
> +    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
> +        flags |= VIRGL_RENDERER_DRM;
> +
> +        if (!gl->context_fence_enabled) {
> +            /*
> +             * Virglrenderer skips enabling DRM context support without
> +             * enabled async-fence feature. VirtIO-GPU will initialize
> +             * successfully, but DRM context won't be available in guest.
> +             */
> +            error_report("DRM native context requires EGL display");
> +            return -EINVAL;
> +        }
> +    }
>  #endif
>  
>      ret = virgl_renderer_init(g, flags, &virtio_gpu_3d_cbs);
> @@ -1294,5 +1307,14 @@ GArray *virtio_gpu_virgl_get_capsets(VirtIOGPU *g)
>          }
>      }
>  
> +    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
> +        virgl_renderer_get_cap_set(VIRTIO_GPU_CAPSET_DRM,
> +                                   &capset_max_ver,
> +                                   &capset_max_size);
> +        if (capset_max_size) {
> +            virtio_gpu_virgl_add_capset(capset_ids, VIRTIO_GPU_CAPSET_DRM);
> +        }
> +    }
> +
>      return capset_ids;
>  }
> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> index c0570ef8565a..c1acafe6246b 100644
> --- a/hw/display/virtio-gpu.c
> +++ b/hw/display/virtio-gpu.c
> @@ -1492,6 +1492,21 @@ void virtio_gpu_device_realize(DeviceState *qdev, Error **errp)
>  #endif
>      }
>  
> +    if (virtio_gpu_drm_enabled(g->parent_obj.conf)) {
> +#ifdef VIRGL_VERSION_MAJOR
> +    #if VIRGL_VERSION_MAJOR >= 1
> +        if (!virtio_gpu_blob_enabled(g->parent_obj.conf) ||
> +            !virtio_gpu_hostmem_enabled(g->parent_obj.conf)) {
> +            error_setg(errp, "drm requires enabled blob and hostmem options");
> +            return;
> +        }
> +    #else
> +        error_setg(errp, "old virglrenderer, drm unsupported");
> +        return;
> +    #endif
> +#endif
> +    }
> +
>      if (!virtio_gpu_base_device_realize(qdev,
>                                          virtio_gpu_handle_ctrl_cb,
>                                          virtio_gpu_handle_cursor_cb,
> diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
> index 99cc6286f473..f1799fcb6eee 100644
> --- a/include/hw/virtio/virtio-gpu.h
> +++ b/include/hw/virtio/virtio-gpu.h
> @@ -98,6 +98,7 @@ enum virtio_gpu_base_conf_flags {
>      VIRTIO_GPU_FLAG_CONTEXT_INIT_ENABLED,
>      VIRTIO_GPU_FLAG_RUTABAGA_ENABLED,
>      VIRTIO_GPU_FLAG_VENUS_ENABLED,
> +    VIRTIO_GPU_FLAG_DRM_ENABLED,
>  };
>  
>  #define virtio_gpu_virgl_enabled(_cfg) \
> @@ -118,6 +119,8 @@ enum virtio_gpu_base_conf_flags {
>      (_cfg.hostmem > 0)
>  #define virtio_gpu_venus_enabled(_cfg) \
>      (_cfg.flags & (1 << VIRTIO_GPU_FLAG_VENUS_ENABLED))
> +#define virtio_gpu_drm_enabled(_cfg) \
> +    (_cfg.flags & (1 << VIRTIO_GPU_FLAG_DRM_ENABLED))
>  
>  struct virtio_gpu_base_conf {
>      uint32_t max_outputs;

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro