VHost Net
feature moves the task of converting virtio descriptors to skbs and back from qemu userspace to the kernel driver. This was shown to reduce latency by a factor of five, and improve bandwidth from 90% native to 95% of native on some systems.
-netdev
options (instead of -net) and adding the vhost=on
flag.
virtio-console
pci device is now equipped to handle multiple console ports as well as generic ports for guests running on top of qemu and KVM. This facilitates simple communication between guest and host.