Hi,
For ad-hoc usage such as with desktop virt, then I think users would typically want to use have PCI devices re-assigned to host at shutdown for the most part.
Unfortunately that tends to not work very well for some kinds of devices. I have an explicit "managed=no" in my configs, otherwise I risk the igd (intel gfx) hangs the system when assigning it back to the host.
If apps change to use managed=detach then they will only work with new libvirt, where as if they change to use the virNodeDeviceDetach() API they'll work with all historic version of libvirt that support PCI assignment.
My "app" is "virsh edit" ;) So, I have to do an explicit "virsh nodedev-detach" before I can start the guest. Yes, it's annonying. But guest failing to start is better than host crashing on guest shutdown in case I forget to do it. And, no, I don't want do that in the boot scripts somewhere because I might want to use the igd on the host. "managed=detach" would be a very nice solution to that problem. cheers, Gerd