This output from "ovs-vsctl list interface vnet0" shows how to match an OVS interface to a specific VM using the MAC address stored in the external_ids value.

ovs-vsctl-list-interface

_uuid               : d3613f46-4ef8-4e4c-99f6-55676394a32a
admin_state         : up
cfm_fault           : []
cfm_fault_status    : []
cfm_health          : []
cfm_mpid            : []
cfm_remote_mpids    : []
cfm_remote_opstate  : []
duplex              : full
external_ids        : {attached-mac="52:54:00:B5:AE:29", iface-id="d198ac1a-c93e-af49-a0f0-ad78a5b19a56", iface-status=active, vm-id="c0e9b909-7233-d2eb-7fde-3a2d39db1ae5"}
ingress_policing_burst: 0
ingress_policing_rate: 0
lacp_current        : []
link_resets         : 1
link_speed          : 10000000
link_state          : up
mac                 : []
mac_in_use          : "fe:54:00:b5:ae:29"
mtu                 : 1500
name                : "vnet0"
ofport              : 2
ofport_request      : []
options             : {}
other_config        : {}
statistics          : {collisions=0, rx_bytes=10322, rx_crc_err=0, rx_dropped=0, rx_errors=0, rx_frame_err=0, rx_over_err=0, rx_packets=141, tx_bytes=6790, tx_dropped=0, tx_errors=0, tx_packets=79}
status              : {driver_name=tun, driver_version="1.6", firmware_version="N/A"}
type                : ""