On Thu, Oct 22, 2015 at 02:32:31PM +0300, Michael S. Tsirkin wrote: > On Thu, Oct 22, 2015 at 05:49:55PM +0800, Yuanhan Liu wrote: > > On Wed, Oct 21, 2015 at 05:26:18PM +0300, Michael S. Tsirkin wrote: > > > On Wed, Oct 21, 2015 at 08:48:15PM +0800, Yuanhan Liu wrote: > > > > > Please note that for virtio devices, guest is supposed to > > > > > control the placement of incoming packets in RX queues. > > > > > > > > I may not follow you. > > > > > > > > Enqueuing packets to a RX queue is done at vhost lib, outside the > > > > guest, how could the guest take the control here? > > > > > > > > --yliu > > > > > > vhost should do what guest told it to. > > > > > > See virtio spec: > > > 5.1.6.5.5 Automatic receive steering in multiqueue mode > > > > Spec says: > > > > After the driver transmitted a packet of a flow on transmitqX, > > the device SHOULD cause incoming packets for that flow to be > > steered to receiveqX. > > > > > > Michael, I still have no idea how vhost could know the flow even > > after discussion with Huawei. Could you be more specific about > > this? Say, how could guest know that? And how could guest tell > > vhost which RX is gonna to use? > > > > Thanks. > > > > --yliu > > I don't really understand the question. > > When guests transmits a packet, it makes a decision > about the flow to use, and maps that to a tx/rx pair of queues. > > It sends packets out on the tx queue and expects device to > return packets from the same flow on the rx queue.
Why? I can understand that there should be a mapping between flows and queues in a way that there is no re-ordering, but I can't see the relation of receiving a flow with a TX queue. fbl > During transmit, device needs to figure out the flow > of packets as they are received from guest, and track > which flows go on which tx queue. > When it selects the rx queue, it has to use the same table. > > There is currently no provision for controlling > steering for uni-directional > flows which are possible e.g. with UDP. > > We might solve this in a future spec - for example, set a flag notifying > guest that steering information is missing for a given flow, for example > by setting a flag in a packet, or using the command queue, and have > guest send a dummy empty packet to set steering rule for this flow. > > > -- > MST >
