If you try: # dpdk-testpmd --log-level=pmd.net.tap:debug -l 1-2 --vdev=net_tap0 -- -i --rxq=8 --txq=8 It will fail because: EAL: Detected CPU lcores: 8 EAL: Detected NUMA nodes: 1 EAL: Detected static linkage of DPDK EAL: Multi-process socket /var/run/dpdk/rte/mp_socket EAL: Selected IOVA mode 'VA' rte_pmd_tap_probe(): Initializing pmd_tap for net_tap0 eth_dev_tap_create(): TAP device on numa 0 tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tun_alloc(): Using rt-signal 35 eth_dev_tap_create(): allocated dtap0 Interactive-mode selected testpmd: create a new mbuf pool <mb_pool_0>: n=155456, size=2176, socket=0 testpmd: preferred mempool ops selected: ring_mp_mc Warning! port-topology=paired and odd forward ports number, the last port will pair with itself. Configuring Port 0 (socket 0) tap_dev_configure(): net_tap0: dtap0: TX configured queues number: 8 tap_dev_configure(): net_tap0: dtap0: RX configured queues number: 8 tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 0 fd 26 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 0 on fd 26 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 1 fd 212 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 1 on fd 212 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 2 fd 213 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 2 on fd 213 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 3 fd 214 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 3 on fd 214 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 4 fd 215 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 4 on fd 215 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 5 fd 216 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 5 on fd 216 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 6 fd 217 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 6 on fd 217 csum off tun_alloc(): /dev/net/tun Features 00007173 tun_alloc(): Multi-queue support for 16 queues tun_alloc(): Device name is 'dtap0' tap_setup_queue(): dtap0: add tx queue for qid 7 fd 218 tap_tx_queue_setup(): TX TUNTAP device name dtap0, qid 7 on fd 218 csum off tap_setup_queue(): dtap0: dup fd 26 for rx queue qid 0 (219) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 0 on fd 219 tap_setup_queue(): dtap0: dup fd 212 for rx queue qid 1 (220) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 1 on fd 220 tap_setup_queue(): dtap0: dup fd 213 for rx queue qid 2 (221) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 2 on fd 221 tap_setup_queue(): dtap0: dup fd 214 for rx queue qid 3 (222) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 3 on fd 222 tap_setup_queue(): dtap0: dup fd 215 for rx queue qid 4 (223) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 4 on fd 223 tap_setup_queue(): dtap0: dup fd 216 for rx queue qid 5 (224) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 5 on fd 224 tap_setup_queue(): dtap0: dup fd 217 for rx queue qid 6 (225) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 6 on fd 225 tap_setup_queue(): dtap0: dup fd 218 for rx queue qid 7 (226) tap_rx_queue_setup(): RX TUNTAP device name dtap0, qid 7 on fd 226 EAL: Cannot send more than 8 FDs tap_mp_req_on_rxtx(): Failed to send start req to secondary 7 This is a regression caused by: commit c36ce7099c2187926cd62cff7ebd479823554929 Author: Kumara Parameshwaran <kumaraparamesh92@gmail.com> Date: Mon Jan 31 20:02:34 2022 +0530 net/tap: fix to populate FDs in secondary process When a tap device is hotplugged to primary process which in turn adds the device to all secondary process, the secondary process does a tap_mp_attach_queues, but the fds are not populated in the primary during the probe they are populated during the queue_setup, added a fix to sync the queues during rte_eth_dev_start Fixes: 4852aa8f6e21 ("drivers/net: enable hotplug on secondary process") Cc: stable@dpdk.org Signed-off-by: Kumara Parameshwaran <kparameshwar@vmware.com> Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>