Hello, I just received this bug report:
https://bugzilla.suse.com/show_bug.cgi?id=1066757 The reporter runs a live migration of a kvm guest from a host with kernel supporting UFO (openSUSE 42.2 or 42.3, based on 4.4) to a host with kernel with UFO support removed (SLE15 or openSUSE 15.0 pre-release which is based on 4.12 but has the UFO removal series backported). The migration fails with kvm: virtio-net: saved image requires TUN_F_UFO support because the guest image has a virtio_net device with UFO enabled which requires TUN_F_UFO on the corresponding host tun device but that is no longer available on the target host. This kind of problem already happened once: https://www.spinics.net/lists/netdev/msg443821.html At that time, commit 3d0ad09412ff ("drivers/net: Disable UFO through virtio") was reverted once the issue it worked around was resolved in a different way. I didn't have time to think it through yet but perhaps we could allow setting TUN_F_UFO and ignore its value. This is not time critical for SLE15 / openSUSE 15.0 which are still at early beta stage but 4.14 final is close and once it's out, more users are going to hit this. Michal Kubecek
