Users can create the desired number of RxQ and TxQ in DPDK. For example, if the number of RxQ = 2 and the number of TxQ = 5, a total of 8 file descriptors will be created for a tap device, including RxQ, TxQ, and one for keepalive [1]. The RxQ and TxQ with the same ID are paired by dup(2) [2].
In this scenario, Kernel will have 3 RxQ where packets are incoming but not read. The reason for this is that there are only 2 RxQ that are polled by DPDK, while there are 5 queues in the kernel. This patch add a checking if DPDK has appropriate numbers of queues to avoid unexpected packet drop. I had first discussed this issue in OVS [3], but changed my mind that a fix in DPDK would be more appropriate. [1]: https://github.com/DPDK/dpdk/blob/0c6e27549c/drivers/net/tap/rte_eth_tap.c#L1967-L1973 [2]: https://github.com/DPDK/dpdk/blob/0c6e27549c/drivers/net/tap/rte_eth_tap.c#L1465-L1466 [3]: https://mail.openvswitch.org/pipermail/ovs-dev/2021-November/389690.html Signed-off-by: Nobuhiro MIKI <nm...@yahoo-corp.jp> --- drivers/net/tap/rte_eth_tap.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c index f1b48cae82..f0090a604d 100644 --- a/drivers/net/tap/rte_eth_tap.c +++ b/drivers/net/tap/rte_eth_tap.c @@ -940,6 +940,14 @@ tap_dev_configure(struct rte_eth_dev *dev) RTE_PMD_TAP_MAX_QUEUES); return -1; } + if (dev->data->nb_rx_queues != dev->data->nb_tx_queues) { + TAP_LOG(ERR, + "%s: number of rx queues %d must be equal to number of tx queues %d", + dev->device->name, + dev->data->nb_rx_queues, + dev->data->nb_tx_queues); + return -1; + } TAP_LOG(INFO, "%s: %s: TX configured queues number: %u", dev->device->name, pmd->name, dev->data->nb_tx_queues); -- 2.24.4
