On Mon, Jun 15, 2015 at 03:43:13PM +0800, Jason Wang wrote: > > > On 06/12/2015 10:28 PM, Michael S. Tsirkin wrote: > > On Fri, Jun 12, 2015 at 03:55:33PM +0800, Jason Wang wrote: > >> > >> On 06/11/2015 08:13 PM, Michael S. Tsirkin wrote: > >>> On Thu, Jun 11, 2015 at 02:10:48PM +0200, Thibaut Collet wrote: > >>>> I am not sure to understand your remark: > >>>> > >>>>> It needs to be sent when backend is activated by guest kick > >>>>> (in case of virtio 1, it's possible to use DRIVER_OK for this). > >>>>> This does not happen when VM still runs on source. > >>>> Could you confirm rarp can be sent by backend when the > >>>> VHOST_USER_SET_VRING_KICK message is received by the backend ? > >>> No - the time to send pakets is when you start processing > >>> the rings. > >>> > >>> And the time to do that is when you detect a kick on > >>> an eventfd, not when said fd is set. > >>> > >> Probably not. What if guest is only doing receiving? > > Clarification: the kick can be on any VQs. > > In your example, guest kicks after adding receive buffers. > > Yes, but refill only happens on we are lacking of receive buffers. It is > not guaranteed to happen just after migration, we may have still have > enough rx buffers for device to receive.
I think we also kick the backend after migration, do we not? Further, DRIVER_OK can be used as a signal to start backend too. > > > >> In this case, you > >> won't detect any kick if you don't send the rarp first.