On Wed, Sep 09, 2015 at 01:09:52AM +0200, marcandre.lur...@redhat.com wrote: > From: Marc-André Lureau <marcandre.lur...@redhat.com> > > In a previous series "Add feature to start QEMU without vhost-user > backend", Tetsuya Mukawa proposed to allow the vhost-user backend to > disconnect and reconnect. However, Michael Tsirkin pointed out that > you can't do that without extra care, because the guest and hypervisor > don't know the slave ring manipulation state, there might be pending > replies for example that could be lost, and suggested to reset the > guest queues, but this requires kernel changes, and it may have to > clear the ring and lose queued packets. > > The following series starts from the idea that the slave can request a > "managed" shutdown instead and later recover (I guess the use case for > this is to allow for example to update static dispatching/filter rules > etc)
I'm still not sure users actually need this. I am inclined to think we should teach guests to respond to NEED_RESET status. Then to handle disconnect, we would - deactivate the disconnected backend - stop VM, and wait for a reconnect - set NEED_RESET status, and re-activate the backend after guest reset -- MST
