drm/qxl: Pin buffer objects for internal mappings

Add qxl_bo_pin_and_vmap() that pins and vmaps a buffer object in one
step. Update callers of the regular qxl_bo_vmap(). Fixes a bug where
qxl accesses an unpinned buffer object while it is being moved; such
as with the monitor-description BO. An typical error is shown below.

[ 4.303586] [drm:drm_atomic_helper_commit_planes] *ERROR* head 1 wrong: 65376256x16777216+0+0
[ 4.586883] [drm:drm_atomic_helper_commit_planes] *ERROR* head 1 wrong: 65376256x16777216+0+0
[ 4.904036] [drm:drm_atomic_helper_commit_planes] *ERROR* head 1 wrong: 65335296x16777216+0+0
[ 5.374347] [drm:qxl_release_from_id_locked] *ERROR* failed to find id in release_idr

Commit b33651a5c98d ("drm/qxl: Do not pin buffer objects for vmap")
removed the implicit pin operation from qxl's vmap code. This is the
correct behavior for GEM and PRIME interfaces, but the pin is still
needed for qxl internal operation.

Also add a corresponding function qxl_bo_vunmap_and_unpin() and remove
the old qxl_bo_vmap() helpers.

Future directions: BOs should not be pinned or vmapped unnecessarily.
The pin-and-vmap operation should be removed from the driver and a
temporary mapping should be established with a vmap_local-like helper.
See the client helper drm_client_buffer_vmap_local() for semantics.

v2:
- unreserve BO on errors in qxl_bo_pin_and_vmap() (Dmitry)

Signed-off-by: Thomas Zimmermann <[e-mail]>
Fixes: b33651a5c98d ("drm/qxl: Do not pin buffer objects for vmap")
Reported-by: David Kaplan <[e-mail]>
Closes: https://lore.kernel.org/dri-devel/[e-mail]/
Tested-by: David Kaplan <[e-mail]>
Reviewed-by: Daniel Vetter <[e-mail]>
Cc: Thomas Zimmermann <[e-mail]>
Cc: Dmitry Osipenko <[e-mail]>
Cc: Christian König <[e-mail]>
Cc: Zack Rusin <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Cc: Gerd Hoffmann <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Reviewed-by: Dmitry Osipenko <[e-mail]>
Reviewed-by: Zack Rusin <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/qxl/qxl_display.c

···
 	if (ret)
 		goto err;
 
-	ret = qxl_bo_vmap(cursor_bo, &cursor_map);
+	ret = qxl_bo_pin_and_vmap(cursor_bo, &cursor_map);
 	if (ret)
 		goto err_unref;
 
-	ret = qxl_bo_vmap(user_bo, &user_map);
+	ret = qxl_bo_pin_and_vmap(user_bo, &user_map);
 	if (ret)
 		goto err_unmap;
 
···
 		       user_map.vaddr, size);
 	}
 
-	qxl_bo_vunmap(user_bo);
-	qxl_bo_vunmap(cursor_bo);
+	qxl_bo_vunmap_and_unpin(user_bo);
+	qxl_bo_vunmap_and_unpin(cursor_bo);
 	return cursor_bo;
 
 err_unmap:
-	qxl_bo_vunmap(cursor_bo);
+	qxl_bo_vunmap_and_unpin(cursor_bo);
 err_unref:
 	qxl_bo_unpin(cursor_bo);
 	qxl_bo_unref(&cursor_bo);
···
 	}
 	qdev->monitors_config_bo = gem_to_qxl_bo(gobj);
 
-	ret = qxl_bo_vmap(qdev->monitors_config_bo, &map);
+	ret = qxl_bo_pin_and_vmap(qdev->monitors_config_bo, &map);
 	if (ret)
 		return ret;
 
···
 	qdev->monitors_config = NULL;
 	qdev->ram_header->monitors_config = 0;
 
-	ret = qxl_bo_vunmap(qdev->monitors_config_bo);
+	ret = qxl_bo_vunmap_and_unpin(qdev->monitors_config_bo);
 	if (ret)
 		return ret;
 

drivers/gpu/drm/qxl/qxl_object.c

···
 	return 0;
 }
 
-int qxl_bo_vmap(struct qxl_bo *bo, struct iosys_map *map)
+int qxl_bo_pin_and_vmap(struct qxl_bo *bo, struct iosys_map *map)
 {
 	int r;
 
···
 	if (r)
 		return r;
 
+	r = qxl_bo_pin_locked(bo);
+	if (r) {
+		qxl_bo_unreserve(bo);
+		return r;
+	}
+
 	r = qxl_bo_vmap_locked(bo, map);
+	if (r)
+		qxl_bo_unpin_locked(bo);
 	qxl_bo_unreserve(bo);
 	return r;
 }
···
 	ttm_bo_vunmap(&bo->tbo, &bo->map);
 }
 
-int qxl_bo_vunmap(struct qxl_bo *bo)
+int qxl_bo_vunmap_and_unpin(struct qxl_bo *bo)
 {
 	int r;
 
···
 		return r;
 
 	qxl_bo_vunmap_locked(bo);
+	qxl_bo_unpin_locked(bo);
 	qxl_bo_unreserve(bo);
 	return 0;
 }

drivers/gpu/drm/qxl/qxl_object.h

···
 			 u32 priority,
 			 struct qxl_surface *surf,
 			 struct qxl_bo **bo_ptr);
-int qxl_bo_vmap(struct qxl_bo *bo, struct iosys_map *map);
+int qxl_bo_pin_and_vmap(struct qxl_bo *bo, struct iosys_map *map);
 int qxl_bo_vmap_locked(struct qxl_bo *bo, struct iosys_map *map);
-int qxl_bo_vunmap(struct qxl_bo *bo);
+int qxl_bo_vunmap_and_unpin(struct qxl_bo *bo);
 void qxl_bo_vunmap_locked(struct qxl_bo *bo);
 void *qxl_bo_kmap_atomic_page(struct qxl_device *qdev, struct qxl_bo *bo, int page_offset);
 void qxl_bo_kunmap_atomic_page(struct qxl_device *qdev, struct qxl_bo *bo, void *map);