AWS docs state that you need to build the source to get enhanced networking enabled for Ubuntu AMIs: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/sriov-networking.html#enhanced-networking-ubuntu
The current AMI for us-west-2 xenial, ami-835b4efa, fails with:
Building module:
cleaning build area....
cd src/; make BUILD_KERNEL=4.4.0-1020-aws....(bad exit status: 2)
ERROR (dkms apport): binary package for ixgbevf: 3.1.2 not found
Error! Bad return status for module build on kernel: 4.4.0-1020-aws (x86_64)
Consult /var/lib/dkms/ixgbevf/3.1.2/build/make.log for more information.