Man, it took me a while to figure out how to do this! Over on Attaching a Virtual NIC Directly to a Physical Interface I figured out I could use this XML in Virtual Machine Manager (virt-manager) for my NIC device:

<interface type='direct'>
  <source dev='enp9s0' mode='bridge'/>
</interface>

That then gets expanded automatically to something like this:

<interface type="direct">
  <mac address="52:54:00:ce:5b:09"/>
  <source dev="enp9s0" mode="bridge"/>
  <target dev="macvtap4"/>
  <model type="rtl8139"/>
  <alias name="net0"/>
  <address type="pci" domain="0x0000" bus="0x10" slot="0x01" function="0x0"/>
</interface>

Update: ah, balls. This doesn’t completely work, because the guest can’t connect to the host, and vice versa, even though both the host and the guest can connect to the internet. This is a problem for another day. Maybe this or this will help?