Re: [PATCH v1 6/6] virtio-gpu: Support DRM native context

[Akihiko Odaki <akihiko.odaki@daynix.com>]

On 2024/10/07 8:23, Dmitry Osipenko wrote:
> Add support for DRM native contexts to VirtIO-GPU. DRM context is enabled
> using a new virtio-gpu-gl device option "drm=true".
> 
> 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      | 12 ++++++++++++
>   hw/display/virtio-gpu.c            | 15 +++++++++++++++
>   include/hw/virtio/virtio-gpu.h     |  3 +++
>   5 files changed, 43 insertions(+)
> 
> diff --git a/docs/system/devices/virtio-gpu.rst b/docs/system/devices/virtio-gpu.rst
> index b7eb0fc0e727..8ce67c98aae2 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=true,drm=true

"on" is more commonly used than "true".

> +
> +.. _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 ad1d40901bff..d61f78a28881 100644
> --- a/hw/display/virtio-gpu-virgl.c
> +++ b/hw/display/virtio-gpu-virgl.c
> @@ -1227,6 +1227,18 @@ 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.
> +             */
> +            warn_report("DRM native context requires EGL display");

It should report an error and stop when an explicitly requested feature 
is unavailable.

> +        }
> +    }
>   #endif
>   
>       ret = virgl_renderer_init(g, flags, &virtio_gpu_3d_cbs);
> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> index 0d1de7dc398c..cfd4ed8a104f 100644
> --- a/hw/display/virtio-gpu.c
> +++ b/hw/display/virtio-gpu.c
> @@ -1521,6 +1521,21 @@ 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 e95d1619c885..6aaf27d1b319 100644
> --- a/include/hw/virtio/virtio-gpu.h
> +++ b/include/hw/virtio/virtio-gpu.h
> @@ -100,6 +100,7 @@ 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) \
> @@ -120,6 +121,8 @@ 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;