* Michael S. Tsirkin (m...@redhat.com) wrote: > On Fri, May 31, 2019 at 02:01:54PM -0300, Eduardo Habkost wrote: > > > Yes. It's just lots of extremely low level interfaces > > > and all rather pointless. > > > > > > And down the road extensions like surprise removal support will make it > > > all cleaner and more transparent. Floating things up to libvirt means > > > all these low level details will require more and more hacks. > > > > Why do you call it pointless? > > We'd need APIs to manipulate device visibility to guest, hotplug > controller state and separately manipulate the resources allocated. This > is low level stuff that users really have no idea what to do about. > Exposing such a level of detail to management is imho pointless. > We are better off with a high level API, see below.
so I don't know much about vfio; but to me it strikes me that you wouldn't need that low level detail if we just reworked vfio to look more like all our other devices; something like: -vfiodev host=02:00.0,id=gpu -device vfio-pci,dev=gpu The 'vfiodev' would own the resources; so to do this trick, the management layer would: hotunplug the vfio-pci migrate if anything went wrong it would hotplug the vfio-pci backin you wouldn't have free'd up any resources because they belonged to the vfiodev. > > If we want this to work before > > surprise removal is implemented, we need to provide an API that > > works for management software. > > Don't we want to make this work > > without surprise removal too? > > This patchset adds an optional, off by default support for > migrating guests with an assigned network device. > If enabled this requires guest to allow migration. > > Of course this can be viewed as a security problem since it allows guest > to block migration. We can't detect a malicious guest reliably imho. > What we can do is report to management when guest allows migration. > Policy such what to do when this does not happen for a while and > what timeout to set would be up to management. > > The API in question would be a high level one, something > along the lines of a single "guest allowed migration" event. This is all fairly normal problems with hot unplugging - that's already dealt with at higher levels for normal hot unplugging. The question here is to try to avoid duplicating that fairly painful process in qemu. Dave > > -- > MST -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
