This patch makes userspace can get and set backend features to
vhost-vdpa.
Signed-off-by: NCindy Lu <lulu@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20200804162048.22587-4-eli@mellanox.comSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>