os-vif focal/ussuri:

$ uname -a
Linux node-laveran 5.4.0-84-generic #94-Ubuntu SMP Thu Aug 26 20:27:37 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

$ dpkg -l | grep os-vif
ii  python3-os-vif                       2.0.0-0ubuntu2                                       all          Integration library between network and compute - Python 3.x

$ sudo grep -A6 hostdev /etc/libvirt/qemu/instance-00000002.xml
    <interface type='hostdev' managed='yes'>
      <mac address='fa:16:3e:66:37:f9'/>
      <source>
        <address type='pci' domain='0x0000' bus='0x03' slot='0x03' function='0x7'/>
      </source>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>

$ sudo ovs-vsctl find interface name=eth29
_uuid               : cce9cf12-28e2-4c4c-be49-6231eaac991c
admin_state         : up
bfd                 : {}
bfd_status          : {}
cfm_fault           : []
cfm_fault_status    : []
cfm_flap_count      : []
cfm_health          : []
cfm_mpid            : []
cfm_remote_mpids    : []
cfm_remote_opstate  : []
duplex              : []
error               : []
external_ids        : {attached-mac="fa:16:3e:66:37:f9", iface-id="88dc4421-c068-4aea-995e-cf181966f6c8", iface-status=active, vm-uuid="6c0ea8c0-a7aa-4cf4-b879-af2523ea5ee1"}
ifindex             : 104
ingress_policing_burst: 0
ingress_policing_rate: 0
lacp_current        : []
link_resets         : 0
link_speed          : []
link_state          : up
lldp                : {}
mac                 : []
mac_in_use          : "5e:03:fa:49:dc:37"
mtu                 : 8942
mtu_request         : []
name                : eth29
ofport              : 3
ofport_request      : []
options             : {}
other_config        : {}
statistics          : {collisions=0, rx_bytes=65184, rx_crc_err=0, rx_dropped=0, rx_errors=0, rx_frame_err=0, rx_missed_errors=0, rx_over_err=0, rx_packets=446, tx_bytes=93555, tx_dropped=0, tx_errors=0, tx_packets=398}
status              : {driver_name=mlx5e_rep, driver_version="5.4.0-84-generic", firmware_version="16.31.1014 (MT_0000000183)"}
type                : ""

$ sudo ls -l /sys/class/net/eth29/device
ls: cannot access '/sys/class/net/eth29/device': No such file or directory

$ sudo ls -l /sys/class/net/enp129s0f0/device/net/
total 0
drwxr-xr-x 6 root root 0 Sep  9 13:16 enp129s0f0

$ ssh fnord-node-laveran-1 lspci
...
00:03.0 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]

$ sudo apt install --install-recommends linux-generic-hwe-20.04-edge-wip
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  linux-headers-5.13.0-14-generic linux-headers-generic-hwe-20.04-edge-wip
  linux-hwe-5.13-headers-5.13.0-14 linux-image-5.13.0-14-generic
  linux-image-generic-hwe-20.04-edge-wip linux-modules-5.13.0-14-generic
  linux-modules-extra-5.13.0-14-generic
Suggested packages:
  fdutils linux-doc | linux-hwe-5.13-source-5.13.0 linux-hwe-5.13-tools
The following NEW packages will be installed:
  linux-generic-hwe-20.04-edge-wip linux-headers-5.13.0-14-generic
  linux-headers-generic-hwe-20.04-edge-wip linux-hwe-5.13-headers-5.13.0-14
  linux-image-5.13.0-14-generic linux-image-generic-hwe-20.04-edge-wip
  linux-modules-5.13.0-14-generic linux-modules-extra-5.13.0-14-generic
0 upgraded, 8 newly installed, 0 to remove and 57 not upgraded.
Need to get 81.1 MB of archives.
After this operation, 411 MB of additional disk space will be used.
Do you want to continue? [Y/n] 
...

$ sudo shutdown -r now
...

$ uname -a
Linux node-laveran 5.13.0-14-generic #14~20.04.4-Ubuntu SMP Wed Aug 25 11:02:57 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

$ sudo ls -l /sys/class/net/eth29/device
lrwxrwxrwx 1 root root 0 Sep  9 14:01 /sys/class/net/eth29/device -> ../../../0000:03:00.0

$ sudo ls -l /sys/class/net/enp129s0f0/device/net/
total 0
drwxr-xr-x 6 root root 0 Sep  9 13:59 enp129s0f0
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth0
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth1
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth10
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth11
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth12
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth13
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth14
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth15
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth16
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth17
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth18
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth19
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth2
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth20
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth21
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth22
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth23
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth24
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth25
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth26
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth27
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth28
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth29
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth3
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth30
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth31
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth4
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth5
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth6
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth7
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth8
drwxr-xr-x 5 root root 0 Sep  9 14:01 eth9

$ ssh fnord-node-laveran-1 lspci
...
00:03.0 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
...