drm: Disable the cursor plane on atomic contexts with virtualized drivers

drm: Disable the cursor plane on atomic contexts with virtualized drivers

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
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231023074613.41327-2-aesteve@redhat.com