On Fri, May 31, 2019 at 04:43:44PM -0400, Michael S. Tsirkin wrote: > On Fri, May 31, 2019 at 07:45:13PM +0100, Dr. David Alan Gilbert wrote: > > * 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. > > > IIUC that doesn't really work with passthrough > unless guests support surprise removal.
Why? For the guest, this is indistinguishable from the unplug request implemented by this series. -- Eduardo
