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

[Ryosuke Yasuoka <ryasuoka@redhat.com>]

Pass array of pages of the scanout buffer [1] to shmem BO, allowing
drm_panic to work even if the BO is not vmapped.

[1] 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>
---
 drivers/gpu/drm/virtio/virtgpu_plane.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
index a6f5a78f436a..2ff57d559c86 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -500,11 +500,19 @@ 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) || bo->base.base.import_attach || !bo->base.vaddr)
+	if (virtio_gpu_is_vram(bo) || bo->base.base.import_attach)
 		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;

base-commit: e7bb7d44c3b97aea1f0e354c6499900154ac67f2
-- 
2.49.0