It looks like you're trying to pass host devices through to the VM.
Using the recommended(*) virtual devices in a first step would make troubleshooting easier.
For example, you could start with:
qemu-system-x86_64 -enable-kvm -M q35 -cpu host -smp 4 -m 2G \
-boot d -cdrom /home/NetBSD-9.1-amd64.iso \
-hda NetBSD-9.1-amd64-install.img \
-display gtk,gl=on -device virtio-vga \
-nic user,model=virtio-net-pci \
It should work out of the box and you'll then be able to change one option at a time to get exactly what you want.
[Note: using "gtk" as the display option will give you a "View" menu where you can switch between virtio-vga (the VM's screen) and compatmonitor0 (an administration console where you can type cool things such as "sendkey ctlr-alt-f2" - very convenient for troubleshooting)]
(*): The major problem with QEMU is that it is poorly documented and that relevant information is scattered across the web, mostly on blogs. :/