Hi David, On Fri, Sep 17, 2021 at 11:33:44AM +0200, David Marchand wrote: > When attaching to an existing mono queue tap, the virtio-user was not > reporting that the virtio device was not properly initialised which > prevented from starting the port later. > > $ ip tuntap add test mode tap > $ dpdk-testpmd --vdev \ > net_virtio_user0,iface=test,path=/dev/vhost-net,queues=2 -- -i > > ... > virtio_user_dev_init_mac(): (/dev/vhost-net) No valid MAC in devargs or > device, use random > vhost_kernel_open_tap(): TUNSETIFF failed: Invalid argument > vhost_kernel_enable_queue_pair(): fail to open tap for vhost kernel > virtio_user_start_device(): (/dev/vhost-net) Failed to start device > ... > Configuring Port 0 (socket 0) > vhost_kernel_open_tap(): TUNSETIFF failed: Invalid argument > vhost_kernel_enable_queue_pair(): fail to open tap for vhost kernel > virtio_set_multiple_queues(): Multiqueue configured but send command > failed, this is too late now... > Fail to start port 0: Invalid argument > Please stop the ports first > Done > > The virtio-user with vhost-kernel backend was going through a lot > of complications to initialise tap fds only when using them. > > For each qp enabled for the first time, a tapfd was created via > TUNSETIFF with unneeded additional steps (see below) and then mapped to > the right qp in the vhost-net backend. > Unneeded steps (as long as it has been done once for the port): > - tap features were queried while this is a constant on a running > system, > - the device name in DPDK was updated, > - the mac address of the tap was set, > > On subsequent qps state change, the vhost-net backend fd mapping was > updated and the associated queue/tapfd were disabled/enabled via > TUNSETQUEUE. > > Now, this patch simplifies the whole logic by keeping all tapfds opened > and in enabled state (from the tap point of view) at all time. > > Unused ioctl defines are removed. > > Tap features are validated earlier to fail initialisation asap. > Tap name discovery and mac address configuration are moved when > configuring qp 0. > > To support attaching to mono queue tap, the virtio-user driver now tries > to attach in multi queue first, then fallbacks to mono queue. > > Finally (but this is more for consistency), VIRTIO_NET_F_MQ feature is > exposed only if the underlying tap supports multi queue. > > Signed-off-by: David Marchand <david.march...@redhat.com>
It also solves our use-case, which is a bit different: - our application creates a tap with the IFF_MULTI_QUEUE - we bind this tap to a virtio-user pmd Previously, it was not working when passing queues=1 to the pmd, the TUNSETIFF ioctl() in the pmd was failing because the IFF_MULTI_QUEUE flag was not passed. With your patch, it works fine, thanks. (...) > @@ -414,18 +425,40 @@ vhost_kernel_setup(struct virtio_user_dev *dev) > PMD_DRV_LOG(ERR, "fail to open %s, %s", dev->path, > strerror(errno)); > goto err_tapfds; > } > - > data->vhostfds[i] = vhostfd; > } > > + ifname = dev->ifname != NULL ? dev->ifname : "tap%d"; > + if (tap_features & IFF_MULTI_QUEUE) > + data->tapfds[0] = tap_open(ifname, true); > + if (data->tapfds[0] < 0) > + data->tapfds[0] = tap_open(ifname, false); As discussed off-list, since tap_open() is called twice, it can in some conditions log failures twice. And since tun/tap multi queue feature is available from 3.8 kernel, we may not want to bother with that. Olivier
