[libvirt] [RFC] handling hostdev save/load net config for non SR-IOV devices

Hi, I have a PoC that enables partial coldplug assignment of multifunction PCI devices with managed mode. At this moment, Libvirt can't handle this scenario - the code will detach only the hostdevs from the XML, when in fact the whole IOMMU needs to be detached. This can be verified by the fact that Libvirt handles the unmanaged scenario well, as long as the user detaches the whole IOMMU beforehand. I have played with 2 approaches. The one I am planning to contribute back is a change inside virHostdevGetPCIHostDeviceList(), that adds the extra PCI devices for detach/re-attach in case a PCI Multifunction device in managed mode is presented in the XML. Now, there's a catch. Inside both virHostdevPreparePCIDevices() and virHostdevReAttachPCIDevices() there are code to save/restore the network configuration for SR-IOV devices. These functions iterates in the hostdevs list, instead of the pcidevs list I'm changing. The final result, given that the current conditions used for SR-IOV matches the conditions for multifunction PCI devices as well, is that not all virtual functions will get their network configuration saved/restored. For example, a guest that uses 3 of 4 functions of a PCI MultiFunction card, let's say functions 0,1 and 3. The code will handle the detach of all the IOMMU, including the function 2 that isn't declared in the XML. However, since function 2 isn't a hostdev, its network config will not be restored after the VM shutdown. Now comes the question: how much effort should be spent into making the network config of all the functions be restored? Is this a blocker for the whole code to be accepted or, given it is proper documented somewhere, it can be done later on? Thanks, DHB