drm/i915/gvt: remove the extra vfio_device refcounting for dmabufs

All the dmabufs are torn down when th VGPU is released, so there is
no need for extra refcounting here.

Based on an patch from Jason Gunthorpe.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220411141403.86980-25-hch@lst.deReviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>

drivers/gpu/drm/i915/gvt/dmabuf.c

@@ -139,7 +139,6 @@ static void dmabuf_gem_object_free(struct kref *kref)
 			dmabuf_obj = list_entry(pos, struct intel_vgpu_dmabuf_obj, list);
 			if (dmabuf_obj == obj) {
 				list_del(pos);
-				vfio_device_put(vgpu->vfio_device);
 				idr_remove(&vgpu->object_idr,
 					   dmabuf_obj->dmabuf_id);
 				kfree(dmabuf_obj->info);
@@ -473,16 +472,6 @@ int intel_vgpu_query_plane(struct intel_vgpu *vgpu, void *args)
 
 	kref_init(&dmabuf_obj->kref);
 
-	mutex_lock(&vgpu->dmabuf_lock);
-	vgpu->vfio_device = vfio_device_get_from_dev(mdev_dev(vgpu->mdev));
-	if (!vgpu->vfio_device) {
-		gvt_vgpu_err("failed to get vfio device\n");
-		mutex_unlock(&vgpu->dmabuf_lock);
-		ret = -ENODEV;
-		goto out_free_info;
-	}
-	mutex_unlock(&vgpu->dmabuf_lock);
-
 	update_fb_info(gfx_plane_info, &fb_info);
 
 	INIT_LIST_HEAD(&dmabuf_obj->list);
@@ -587,7 +576,6 @@ void intel_vgpu_dmabuf_cleanup(struct intel_vgpu *vgpu)
 		dmabuf_obj->vgpu = NULL;
 
 		idr_remove(&vgpu->object_idr, dmabuf_obj->dmabuf_id);
-		vfio_device_put(vgpu->vfio_device);
 		list_del(pos);
 
 		/* dmabuf_obj might be freed in dmabuf_obj_put */

drivers/gpu/drm/i915/gvt/gvt.h

@@ -231,7 +231,6 @@ struct intel_vgpu {
 	struct kvm *kvm;
 	struct work_struct release_work;
 	atomic_t released;
-	struct vfio_device *vfio_device;
 	struct vfio_group *vfio_group;
 
 	struct kvm_page_track_notifier_node track_node;