On Mon, Dec 03, 2012 at 06:01:58PM +0800, Jason Wang wrote: > On 12/03/2012 05:47 PM, Michael S. Tsirkin wrote: > > On Mon, Dec 03, 2012 at 02:05:27PM +0800, Jason Wang wrote: > >> On Monday, December 03, 2012 12:34:08 PM Rusty Russell wrote: > >>> Jason Wang <jasowang@xxxxxxxxxx> writes: > >>>> +static const struct ethtool_ops virtnet_ethtool_ops; > >>>> + > >>>> +/* > >>>> + * Converting between virtqueue no. and kernel tx/rx queue no. > >>>> + * 0:rx0 1:tx0 2:cvq 3:rx1 4:tx1 ... 2N+1:rxN 2N+2:txN > >>>> + */ > >>>> +static int vq2txq(struct virtqueue *vq) > >>>> +{ > >>>> + int index = virtqueue_get_queue_index(vq); > >>>> + return index == 1 ? 0 : (index - 2) / 2; > >>>> +} > >>>> + > >>>> +static int txq2vq(int txq) > >>>> +{ > >>>> + return txq ? 2 * txq + 2 : 1; > >>>> +} > >>>> + > >>>> +static int vq2rxq(struct virtqueue *vq) > >>>> +{ > >>>> + int index = virtqueue_get_queue_index(vq); > >>>> + return index ? (index - 1) / 2 : 0; > >>>> +} > >>>> + > >>>> +static int rxq2vq(int rxq) > >>>> +{ > >>>> + return rxq ? 2 * rxq + 1 : 0; > >>>> +} > >>>> + > >>> I thought MST changed the proposed spec to make the control queue always > >>> the last one, so this logic becomes trivial. > >> But it may break the support of legacy guest. If we boot a legacy single queue > >> guest on a 2 queue virtio-net device. It may think vq 2 is cvq which is indeed > >> rx1. > > Legacy guyest support should be handled by host using feature > > bits in the usual way: host should detect legacy guest > > by checking the VIRTIO_NET_F_RFS feature. > > > > If VIRTIO_NET_F_RFS is acked, cvq is vq max_virtqueue_pairs * 2. > > If it's not acked, cvq is vq 2. > > > > We could, but we didn't gain much from this. It just seems cleaner and easier to understand. > Furthermore, we need also > do the dynamic creation/destroying of virtqueues during feature > negotiation which seems not supported in qemu now. It's not *done* in qemu now, but it seems easy: just call virtio_add_queue for vq2 and on from virtio_net_set_features. As features can be modified multiple times, we should add virtio_del_queue and call that beforehand to get to the known state (two vqs). -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html