On 1/12/2022 7:23 AM, Nobuhiro MIKI wrote:
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. The RxQ and TxQ
with the same ID are paired by dup(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 Kernel.
This patch add a checking if DPDK has appropriate numbers of
queues to avoid unexpected packet drop.
Signed-off-by: Nobuhiro MIKI <nm...@yahoo-corp.jp>
It makes sense to add this check, since the driver logic seem already has
the assumption that Rx & Tx queue numbers will be same.
But can you please update the tap documentation for this limitation/restriction?
'doc/guides/nics/tap.rst'.
---
v2: fix commit message
I had first discussed this issue in OVS [1], but changed my mind
that a fix in DPDK would be more appropriate.
[1]: https://mail.openvswitch.org/pipermail/ovs-dev/2021-November/389690.html
---
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 5bb472f1a6..02eb311e09 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);
