I'm start the win7 vm from an unassigned nvme- after the update to rc4 this:
Execution error
internal error: process exited while connecting to monitor: 2016-08-19T13:33:14.482162Z qemu-system-x86_64: -device vfio-pci,host=00:1f.3,id=hostdev1,bus=pci.0,addr=0x6: vfio: error, group 9 is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.
2016-08-19T13:33:14.482185Z qemu-system-x86_64: -device vfio-pci,host=00:1f.3,id=hostdev1,bus=pci.0,addr=0x6: vfio: failed to get group 9
2016-08-19T13:33:14.482192Z qemu-system-x86_64: -device vfio-pci,host=00:1f.3,id=hostdev1,bus=pci.0,addr=0x6: Device initialization failed