Re: [PATCH v3 1/8] drm: Disable the cursor plane on atomic contexts with virtualized drivers

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Mon, 26 Jun 2023 23:58:32 -0400
Zack Rusin <zack@kde.org> wrote:

> From: Zack Rusin <zackr@vmware.com>
> 
> Cursor planes on virtualized drivers have special meaning and require
> that the clients handle them in specific ways, e.g. the cursor plane
> should react to the mouse movement the way a mouse cursor would be
> expected to and the client is required to set hotspot properties on it
> in order for the mouse events to be routed correctly.
> 
> This breaks the contract as specified by the "universal planes". Fix it
> by disabling the cursor planes on virtualized drivers while adding
> a foundation on top of which it's possible to special case mouse cursor
> planes for clients that want it.
> 
> Disabling the cursor planes makes some kms compositors which were broken,
> e.g. Weston, fallback to software cursor which works fine or at least
> better than currently while having no effect on others, e.g. gnome-shell
> or kwin, which put virtualized drivers on a deny-list when running in
> atomic context to make them fallback to legacy kms and avoid this issue.
> 
> Signed-off-by: Zack Rusin <zackr@vmware.com>
> Fixes: 681e7ec73044 ("drm: Allow userspace to ask for universal plane list (v2)")

Sounds good to me.

Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>


Thanks,
pq



> Cc: <stable@vger.kernel.org> # v5.4+
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Gurchetan Singh <gurchetansingh@chromium.org>
> Cc: Chia-I Wu <olvaffe@gmail.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: virtualization@lists.linux-foundation.org
> Cc: spice-devel@lists.freedesktop.org
> ---
>  drivers/gpu/drm/drm_plane.c          | 13 +++++++++++++
>  drivers/gpu/drm/qxl/qxl_drv.c        |  2 +-
>  drivers/gpu/drm/vboxvideo/vbox_drv.c |  2 +-
>  drivers/gpu/drm/virtio/virtgpu_drv.c |  2 +-
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c  |  2 +-
>  include/drm/drm_drv.h                |  9 +++++++++
>  include/drm/drm_file.h               | 12 ++++++++++++
>  7 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 24e7998d1731..a4a39f4834e2 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -678,6 +678,19 @@ int drm_mode_getplane_res(struct drm_device *dev, void *data,
>  		    !file_priv->universal_planes)
>  			continue;
>  
> +		/*
> +		 * If we're running on a virtualized driver then,
> +		 * unless userspace advertizes support for the
> +		 * virtualized cursor plane, disable cursor planes
> +		 * because they'll be broken due to missing cursor
> +		 * hotspot info.
> +		 */
> +		if (plane->type == DRM_PLANE_TYPE_CURSOR &&
> +		    drm_core_check_feature(dev, DRIVER_CURSOR_HOTSPOT)	&&
> +		    file_priv->atomic &&
> +		    !file_priv->supports_virtualized_cursor_plane)
> +			continue;
> +
>  		if (drm_lease_held(file_priv, plane->base.id)) {
>  			if (count < plane_resp->count_planes &&
>  			    put_user(plane->base.id, plane_ptr + count))
> diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
> index b30ede1cf62d..91930e84a9cd 100644
> --- a/drivers/gpu/drm/qxl/qxl_drv.c
> +++ b/drivers/gpu/drm/qxl/qxl_drv.c
> @@ -283,7 +283,7 @@ static const struct drm_ioctl_desc qxl_ioctls[] = {
>  };
>  
>  static struct drm_driver qxl_driver = {
> -	.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
> +	.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_CURSOR_HOTSPOT,
>  
>  	.dumb_create = qxl_mode_dumb_create,
>  	.dumb_map_offset = drm_gem_ttm_dumb_map_offset,
> diff --git a/drivers/gpu/drm/vboxvideo/vbox_drv.c b/drivers/gpu/drm/vboxvideo/vbox_drv.c
> index 4fee15c97c34..8ecd0863fad7 100644
> --- a/drivers/gpu/drm/vboxvideo/vbox_drv.c
> +++ b/drivers/gpu/drm/vboxvideo/vbox_drv.c
> @@ -172,7 +172,7 @@ DEFINE_DRM_GEM_FOPS(vbox_fops);
>  
>  static const struct drm_driver driver = {
>  	.driver_features =
> -	    DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
> +	    DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC | DRIVER_CURSOR_HOTSPOT,
>  
>  	.fops = &vbox_fops,
>  	.name = DRIVER_NAME,
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index a7ec5a3770da..8f4bb8a4e952 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -176,7 +176,7 @@ static const struct drm_driver driver = {
>  	 * If KMS is disabled DRIVER_MODESET and DRIVER_ATOMIC are masked
>  	 * out via drm_device::driver_features:
>  	 */
> -	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_RENDER | DRIVER_ATOMIC,
> +	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_RENDER | DRIVER_ATOMIC | DRIVER_CURSOR_HOTSPOT,
>  	.open = virtio_gpu_driver_open,
>  	.postclose = virtio_gpu_driver_postclose,
>  
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 8b24ecf60e3e..d3e308fdfd5b 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -1611,7 +1611,7 @@ static const struct file_operations vmwgfx_driver_fops = {
>  
>  static const struct drm_driver driver = {
>  	.driver_features =
> -	DRIVER_MODESET | DRIVER_RENDER | DRIVER_ATOMIC | DRIVER_GEM,
> +	DRIVER_MODESET | DRIVER_RENDER | DRIVER_ATOMIC | DRIVER_GEM | DRIVER_CURSOR_HOTSPOT,
>  	.ioctls = vmw_ioctls,
>  	.num_ioctls = ARRAY_SIZE(vmw_ioctls),
>  	.master_set = vmw_master_set,
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index b77f2c7275b7..8303016665dd 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -104,6 +104,15 @@ enum drm_driver_feature {
>  	 * acceleration should be handled by two drivers that are connected using auxiliary bus.
>  	 */
>  	DRIVER_COMPUTE_ACCEL            = BIT(7),
> +	/**
> +	 * @DRIVER_CURSOR_HOTSPOT:
> +	 *
> +	 * Driver supports and requires cursor hotspot information in the
> +	 * cursor plane (e.g. cursor plane has to actually track the mouse
> +	 * cursor and the clients are required to set hotspot in order for
> +	 * the cursor planes to work correctly).
> +	 */
> +	DRIVER_CURSOR_HOTSPOT           = BIT(8),
>  
>  	/* IMPORTANT: Below are all the legacy flags, add new ones above. */
>  
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 966912053cb0..91cf7f452f86 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -228,6 +228,18 @@ struct drm_file {
>  	 */
>  	bool is_master;
>  
> +	/**
> +	 * @supports_virtualized_cursor_plane:
> +	 *
> +	 * This client is capable of handling the cursor plane with the
> +	 * restrictions imposed on it by the virtualized drivers.
> +	 *
> +	 * This implies that the cursor plane has to behave like a cursor
> +	 * i.e. track cursor movement. It also requires setting of the
> +	 * hotspot properties by the client on the cursor plane.
> +	 */
> +	bool supports_virtualized_cursor_plane;
> +
>  	/**
>  	 * @master:
>  	 *


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