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. > In this case, you > won't detect any kick if you don't send the rarp first.
