I am passing an Intel NIC 

[8086:10d3] 06:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection

through to a VM, but when I try to start the VM I get the following error, not sure what I'm doing wrong.  Any assistance would be appreciated:

 

internal error: process exited while connecting to monitor: 2017-10-17T21:31:14.632470Z qemu-system-x86_64: -device vfio-pci,host=06:00.0,id=hostdev0,bus=pci.2,addr=0x4: vfio: error, group 13 is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.
2017-10-17T21:31:14.632496Z qemu-system-x86_64: -device vfio-pci,host=06:00.0,id=hostdev0,bus=pci.2,addr=0x4: vfio: failed to get group 13
2017-10-17T21:31:14.632515Z qemu-system-x86_64: -device vfio-pci,host=06:00.0,id=hostdev0,bus=pci.2,addr=0x4: Device initialization failed

I believe I solved the problem. I booted with the PCIe ACS Override setting enabled and issue went away. 

 

Is there another way I could have handled this?

Post your diagnostics that will probably show your problem.  My guess from above error message is that you have more than ONE device in an IOMMU group.  You could try ACS Override in VM settings or you could pass through ALL of the devices in the IOMMU group and see if that will let it boot.