[dpdk-dev] [PATCH 3/3] net/qede: prevent crash while changing MTU dynamically

[Rasesh Mody <rasesh.mody@cavium.com>]

From: Harish Patil <harish.patil@qlogic.com>

The driver can handle dynamic MTU change without needing the port to be
stopped explicitly by the application. However, there is currently no
check to prevent I/Os from happening on a different thread while the
port is going thru' reset internally. This patch fixes this issue by
assigning RX/TX burst functions to a dummy function and also reconfigure
RX bufsize for each rx queue based on the new MTU value.

Fixes: 200645ac7909 ("net/qede: set MTU")

Signed-off-by: Harish Patil <harish.patil@qlogic.com>
---
 drivers/net/qede/qede_ethdev.c |   57 ++++++++++++++++++++++++++++++----------
 drivers/net/qede/qede_rxtx.c   |    8 ++++++
 drivers/net/qede/qede_rxtx.h   |    4 +++
 3 files changed, 55 insertions(+), 14 deletions(-)

diff --git a/drivers/net/qede/qede_ethdev.c b/drivers/net/qede/qede_ethdev.c
index e096f63..2f1d2b5 100644
--- a/drivers/net/qede/qede_ethdev.c
+++ b/drivers/net/qede/qede_ethdev.c
@@ -1684,32 +1684,61 @@ static int qede_rss_reta_query(struct rte_eth_dev *eth_dev,
 
 int qede_set_mtu(struct rte_eth_dev *dev, uint16_t mtu)
 {
-	uint32_t frame_size;
-	struct qede_dev *qdev = dev->data->dev_private;
+	struct qede_dev *qdev = QEDE_INIT_QDEV(dev);
+	struct ecore_dev *edev = QEDE_INIT_EDEV(qdev);
 	struct rte_eth_dev_info dev_info = {0};
+	struct qede_fastpath *fp;
+	uint32_t frame_size;
+	uint16_t rx_buf_size;
+	uint16_t bufsz;
+	int i;
 
+	PMD_INIT_FUNC_TRACE(edev);
 	qede_dev_info_get(dev, &dev_info);
-
-	/* VLAN_TAG = 4 */
-	frame_size = mtu + ETHER_HDR_LEN + ETHER_CRC_LEN + 4;
-
-	if ((mtu < ETHER_MIN_MTU) || (frame_size > dev_info.max_rx_pktlen))
+	frame_size = mtu + QEDE_ETH_OVERHEAD;
+	if ((mtu < ETHER_MIN_MTU) || (frame_size > dev_info.max_rx_pktlen)) {
+		DP_ERR(edev, "MTU %u out of range\n", mtu);
 		return -EINVAL;
-
+	}
 	if (!dev->data->scattered_rx &&
-	    frame_size > dev->data->min_rx_buf_size - RTE_PKTMBUF_HEADROOM)
+	    frame_size > dev->data->min_rx_buf_size - RTE_PKTMBUF_HEADROOM) {
+		DP_INFO(edev, "MTU greater than minimum RX buffer size of %u\n",
+			dev->data->min_rx_buf_size);
 		return -EINVAL;
-
+	}
+	/* Temporarily replace I/O functions with dummy ones. It cannot
+	 * be set to NULL because rte_eth_rx_burst() doesn't check for NULL.
+	 */
+	dev->rx_pkt_burst = qede_rxtx_pkts_dummy;
+	dev->tx_pkt_burst = qede_rxtx_pkts_dummy;
+	qede_dev_stop(dev);
+	rte_delay_ms(1000);
+	qdev->mtu = mtu;
+	/* Fix up RX buf size for all queues of the port */
+	for_each_queue(i) {
+		fp = &qdev->fp_array[i];
+		if (fp->type & QEDE_FASTPATH_RX) {
+			bufsz = (uint16_t)rte_pktmbuf_data_room_size(
+				fp->rxq->mb_pool) - RTE_PKTMBUF_HEADROOM;
+			if (dev->data->scattered_rx)
+				rx_buf_size = bufsz + QEDE_ETH_OVERHEAD;
+			else
+				rx_buf_size = mtu + QEDE_ETH_OVERHEAD;
+			rx_buf_size = QEDE_CEIL_TO_CACHE_LINE_SIZE(rx_buf_size);
+			fp->rxq->rx_buf_size = rx_buf_size;
+			DP_INFO(edev, "buf_size adjusted to %u\n", rx_buf_size);
+		}
+	}
+	qede_dev_start(dev);
 	if (frame_size > ETHER_MAX_LEN)
 		dev->data->dev_conf.rxmode.jumbo_frame = 1;
 	else
 		dev->data->dev_conf.rxmode.jumbo_frame = 0;
-
 	/* update max frame size */
 	dev->data->dev_conf.rxmode.max_rx_pkt_len = frame_size;
-	qdev->mtu = mtu;
-	qede_dev_stop(dev);
-	qede_dev_start(dev);
+	/* Reassign back */
+	dev->rx_pkt_burst = qede_recv_pkts;
+	dev->tx_pkt_burst = qede_xmit_pkts;
 
 	return 0;
 }
diff --git a/drivers/net/qede/qede_rxtx.c b/drivers/net/qede/qede_rxtx.c
index 6c2837e..e630326 100644
--- a/drivers/net/qede/qede_rxtx.c
+++ b/drivers/net/qede/qede_rxtx.c
@@ -1937,3 +1937,11 @@ void qede_dev_stop(struct rte_eth_dev *eth_dev)
 
 	DP_INFO(edev, "dev_state is QEDE_DEV_STOP\n");
 }
+
+uint16_t
+qede_rxtx_pkts_dummy(__rte_unused void *p_rxq,
+		     __rte_unused struct rte_mbuf **pkts,
+		     __rte_unused uint16_t nb_pkts)
+{
+	return 0;
+}
diff --git a/drivers/net/qede/qede_rxtx.h b/drivers/net/qede/qede_rxtx.h
index c27632e..eb8174f 100644
--- a/drivers/net/qede/qede_rxtx.h
+++ b/drivers/net/qede/qede_rxtx.h
@@ -265,6 +265,10 @@ uint16_t qede_xmit_prep_pkts(void *p_txq, struct rte_mbuf **tx_pkts,
 uint16_t qede_recv_pkts(void *p_rxq, struct rte_mbuf **rx_pkts,
 			uint16_t nb_pkts);
 
+uint16_t qede_rxtx_pkts_dummy(__rte_unused void *p_rxq,
+			      __rte_unused struct rte_mbuf **pkts,
+			      __rte_unused uint16_t nb_pkts);
+
 /* Fastpath resource alloc/dealloc helpers */
 int qede_alloc_fp_resc(struct qede_dev *qdev);
 
-- 
1.7.10.3