On Thu, Sep 23, 2021 at 5:39 PM Olivier Matz <olivier.m...@6wind.com> wrote: > > 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.
Cool. > > (...) > > > @@ -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. Let me relook at this for v2. Thanks for the test! -- David Marchand
