I already have everything setup successfully on a Windows guest on the same host, and can hot-swap the controller with virsh device-attach/detatch.
I can attach the controller to an OSX Mojave guest, if it is not running. But when attempting to detach the device from the running guest, virsh reports ‘Device detached successfully’, but the device remains attached.
Controller in question is a Inateck KT5001 5 Ports USB 3.0 PCIe.
> sudo virsh detach-device MAIN-OSX --file /tmp/controller.xml
Device detached successfully
/tmp/controller.xml:
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
</source>
<alias name='hostdev2'/>
<address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
</hostdev>