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

[Javier Martinez Canillas <javierm@redhat.com>]

Zack Rusin <zack@kde.org> writes:

Hello Zack,

> 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)")
> 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)	&&

Nit: you have a tab instead of an space before && but this can just be
fixed when applying.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat