In case of i40e -based interface (e.g Intel x700 series NIC) is bind to kernel driver (i40e) and is in state "no-carrier" (<NO-CARRIER,BROADCAST,MULTICAST,UP>) because previously it was disabled via "I40E_AQ_PHY_LINK_ENABLED" call, then VPP during initialization of AVF interface is not re-enabling interface link via i40e driver to up.

This is not an issue in case of vfio-pci/dpdk (in vpp) combination, where "set interface state XY up" is properly enabling link removing no-carrier state.

Carrier state cannot be controlled from systemd-networkd which is using ioctl kernel call IFF_UP.

This issue can be reproduced by running dpdk-testpmd with interface bind to vfio-pci and stopping it. Then initializing AVF interface in VPP is not bringing interface up.

[1] https://github.com/dmarion/i40e/blob/1f67ea01dbcfe15e86cc3535ca45bc395c56be0d/src/i40e_ethtool.c#L1060