I've followed the Redhat Enterprise Linux 7 Using SR-IOV guide, with the following changes made for Ubuntu 14.04 and the fact that the Intel driver set (PROWinx64) doesn't install the drivers automatically.
Make sure to bring the network link state up before you start the virtual machine, or the network driver will report "Network cable unplugged" permanently. igbvf doesn't want to detach on Linux 3.10 on Ubuntu 14.04, so I have blacklisted the module.
options igb max_vfs=7
Download the latest Intel Virtual Function drivers from the Intel site, extract PROWinx64 with your favourite archival program. Then run the following command:
pnputil -a PRO1000\Winx64\NDIS62\v1q62x64.inf
Then you can either go to Device Manager and scan for New hardware changes or restart the virtual machine. Your guest networking should now be working.