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From: Nobuhiro MIKI <nmiki@yahoo-corp.jp>
To: keith.wiles@intel.com
Cc: dev@dpdk.org, i.maximets@ovn.org, dmarchan@redhat.com,
	Nobuhiro MIKI <nmiki@yahoo-corp.jp>
Subject: [PATCH v2 1/1] net/tap: add a check that Rx/Tx have the same num of queues
Date: Wed, 12 Jan 2022 16:23:24 +0900
Message-ID: <20220112072324.30601-1-nmiki@yahoo-corp.jp> (raw)

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 <nmiki@yahoo-corp.jp>
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)
 		return -1;
+	if (dev->data->nb_rx_queues != dev->data->nb_tx_queues) {
+			"%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);

             reply	other threads:[~2022-01-12  7:23 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-12  7:23 Nobuhiro MIKI [this message]
2022-01-18 12:31 ` Ferruh Yigit
2022-01-19  7:49   ` Nobuhiro MIKI

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