mainline inclusion
from mainline-5.2-rc1
commit 60e7f2c3
category: bugfix
bugzilla: 15889
CVE: NA

-------------------------------------------------

During mdev parent registration in mdev_register_device(),
if parent device is duplicate, it releases the reference of existing
parent device.
This is incorrect. Existing parent device should not be touched.

Fixes: 7b96953b ("vfio: Mediated device Core driver")
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NKirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: NMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NXuefeng Wang <wxf.wang@hisilicon.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>