Description of problem:
When creating a new VM in virt-manager the default network is usually the NAT'd network named 'default'

But via the Advanced Options section it is possible to select other networks to attach to the guest in place of the NAT/default network.

However this screen does not seem to show macvtap linked to a physical interface as an option.  So if you want to use macvtap you need to create the VM and then later change the network interface through the VM details page NIC section.

It would be good to add options to the Advanced Options section of the 'Create a new virtual machine' page to show things like:

Host device eth0: macvtap
Host device em0: macvtap
etc, etc

In addition, we'd need to add a new drop down to the Advanced options section that is only enabled when macvtap is selected that allows the user to choose between options like Bridge, VEPA, Passthrough