Description of problem:
When Source device is set to: "Host device lo: macvtap" this message occurs when starting the VM.



Version-Release number of selected component (if applicable):
virt-manager-0.10.0-1.fc19.noarch
qemu-system-x86-1.4.2-4.fc19.x86_64
libvirt-daemon-driver-qemu-1.0.5.2-1.fc19.x86_64
qemu-kvm-1.4.2-4.fc19.x86_64
qemu-common-1.4.2-4.fc19.x86_64
qemu-img-1.4.2-4.fc19.x86_64
qemu-guest-agent-1.4.2-4.fc19.x86_64
kernel 3.10.0-1.fc20.x86_64

How reproducible:
Always


Steps to Reproduce:
1. Create a VM with a NIC whose option Source device: is set to "Host device lo: macvtap"
2. Start the VM

Actual results:
Error. VM doesn't start.

Expected results:
No error, VM starts.

Regression:
If I change the Source device: option to "Host device p5p1: macvtap" this problem doesn't occur.

Additional info:
Error starting domain: operation failed: Unable to create macvlan device

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 100, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 122, in tmpcb
    callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1210, in startup
    self._backend.create()
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 698, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: operation failed: Unable to create macvlan device