howto listen on a SPAN-port without PCI passthru

[AndersN]

I'm trying to run zeek on a VM, but cannot use PCI passthru since the 4-port NIC dosen't support passing just one port to the VM.
Is there a way to use macvtap or forcing the bridge to forward all packets to the vm?
Host is HP DL360p G8 with 4-Port Broadcom NetXtreme BCM5719 nic.