setting guest mtu

I was trying to see if it is possible to automatically set the mtu size for the guest. I am using a tunnel with smaller mtu so when I switch over vm's, it would be nice if they get this tunnel mtu automatically. This config: <interface type='direct'> <source dev='tun1' mode='bridge'/> <model type='virtio'/> <mtu size='1462'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> </interface> Generates this error: error: unsupported configuration: setting MTU on interface type direct is not supported yet Is there another way to set this, like with this host_mtu as mentioned in[1], or can I forget about trying? this? qemu-system-x86-2.0.0-1.el7.6.x86_64 qemu-kvm-1.5.3-173.el7_8.3.x86_64 libvirt-4.5.0-33.el7_8.1.x86_64 [1] https://www.mail-archive.com/libvirt-users@redhat.com/msg10746.html