What is the difference between virtio-net-pci, virtio-net-pci-non-transitional and virtio-net-pci-transitional

[Ahmad Ismail]

I am seeing multiple virtio models for -nic.

% qemu-system-x86_64 -nic model=help | grep virtio
virtio-net-pci
virtio-net-pci-non-transitional
virtio-net-pci-transitional

I want to know the difference between them. When to use what?

Thanks and Best Regards,
Ahmmad Ismail