drm/virtio: Support drm_panic with non-vmapped shmem BO

Pass array of pages of the scanout buffer to shmem BO, allowing
drm_panic to work even if the BO is not vmapped.

Link: https://lore.kernel.org/all/20250407140138.162383-3-jfalempe@redhat.com/
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Ryosuke Yasuoka <ryasuoka@redhat.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
[dmitry.osipenko@collabora.com: rebased on misc-next, fixed minor checkpatch warn]
[dmitry.osipenko@collabora.com: changed commit message to use link tag]
Link: https://lore.kernel.org/all/20250412132012.291837-1-ryasuoka@redhat.com/

diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
index 43e755248977580e710f88e78d7679ab116c7a7e..698ea7adb951170f940a9d26e889faeb13ce5258 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -508,11 +508,19 @@ static int virtio_drm_get_scanout_buffer(struct drm_plane *plane,
 
        bo = gem_to_virtio_gpu_obj(plane->state->fb->obj[0]);
 
-       /* Only support mapped shmem bo */
-       if (virtio_gpu_is_vram(bo) || drm_gem_is_imported(&bo->base.base) || !bo->base.vaddr)
+       if (virtio_gpu_is_vram(bo) || drm_gem_is_imported(&bo->base.base))
                return -ENODEV;
 
-       iosys_map_set_vaddr(&sb->map[0], bo->base.vaddr);
+       if (bo->base.vaddr) {
+               iosys_map_set_vaddr(&sb->map[0], bo->base.vaddr);
+       } else {
+               struct drm_gem_shmem_object *shmem = &bo->base;
+
+               if (!shmem->pages)
+                       return -ENODEV;
+               /* map scanout buffer later */
+               sb->pages = shmem->pages;
+       }
 
        sb->format = plane->state->fb->format;
        sb->height = plane->state->fb->height;