[PATCH v4 1/5] failsafe: fix segfault on hotplug event

[Luc Pelletier <lucp.at.work@gmail.com>]

When the failsafe PMD encounters a hotplug event, it switches its rx/tx
functions to "safe" ones that validate the sub-device's rx/tx functions
before calling them. It switches the rx/tx functions by changing the
function pointers in the rte_eth_dev structure.

Following commit 7a0935239b9e, the rx/tx functions of PMDs are no longer
called through the function pointers in the rte_eth_dev structure. They
are rather called through a flat array named rte_eth_fp_ops. The
function pointers in that array are initialized when the devices start
and are initialized.

When a hotplug event occurs, the function pointers in rte_eth_fp_ops
still point to the "unsafe" rx/tx functions in the failsafe PMD since
they haven't been updated. This results in a segmentation fault because
it ends up using the "unsafe" functions, when the "safe" functions
should have been used.

To fix the problem, the "unsafe" rx/tx functions were completely
removed. The "safe" functions are now always used. Modifying the rx/tx
functions on-the-fly is not supported by DPDK, so this is the correct
approach and should have very minimal impact on performance.

Fixes: 7a0935239b9e ("ethdev: make fast-path functions to use new flat array")
Cc: Konstantin Ananyev <konstantin.ananyev@huawei.com>
Cc: stable@dpdk.org

Signed-off-by: Luc Pelletier <lucp.at.work@gmail.com>
---
 drivers/net/failsafe/failsafe_ether.c   |  2 -
 drivers/net/failsafe/failsafe_private.h |  8 ---
 drivers/net/failsafe/failsafe_rxtx.c    | 83 +------------------------
 3 files changed, 1 insertion(+), 92 deletions(-)

diff --git a/drivers/net/failsafe/failsafe_ether.c b/drivers/net/failsafe/failsafe_ether.c
index 10b90fd837..517126565f 100644
--- a/drivers/net/failsafe/failsafe_ether.c
+++ b/drivers/net/failsafe/failsafe_ether.c
@@ -595,8 +595,6 @@ failsafe_eth_rmv_event_callback(uint16_t port_id __rte_unused,
 	fs_lock(fs_dev(sdev), 0);
 	/* Switch as soon as possible tx_dev. */
 	fs_switch_dev(fs_dev(sdev), sdev);
-	/* Use safe bursts in any case. */
-	failsafe_set_burst_fn(fs_dev(sdev), 1);
 	/*
 	 * Async removal, the sub-PMD will try to unregister
 	 * the callback at the source of the current thread context.
diff --git a/drivers/net/failsafe/failsafe_private.h b/drivers/net/failsafe/failsafe_private.h
index 53a451c1b1..3865f2fc34 100644
--- a/drivers/net/failsafe/failsafe_private.h
+++ b/drivers/net/failsafe/failsafe_private.h
@@ -208,18 +208,11 @@ int failsafe_hotplug_alarm_cancel(struct rte_eth_dev *dev);
 
 /* RX / TX */
 
-void failsafe_set_burst_fn(struct rte_eth_dev *dev, int force_safe);
-
 uint16_t failsafe_rx_burst(void *rxq,
 		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
 uint16_t failsafe_tx_burst(void *txq,
 		struct rte_mbuf **tx_pkts, uint16_t nb_pkts);
 
-uint16_t failsafe_rx_burst_fast(void *rxq,
-		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
-uint16_t failsafe_tx_burst_fast(void *txq,
-		struct rte_mbuf **tx_pkts, uint16_t nb_pkts);
-
 /* ARGS */
 
 int failsafe_args_parse(struct rte_eth_dev *dev, const char *params);
@@ -487,7 +480,6 @@ fs_switch_dev(struct rte_eth_dev *dev,
 	} else {
 		return;
 	}
-	failsafe_set_burst_fn(dev, 0);
 	rte_wmb();
 }
 
diff --git a/drivers/net/failsafe/failsafe_rxtx.c b/drivers/net/failsafe/failsafe_rxtx.c
index fe67293299..707fe60a36 100644
--- a/drivers/net/failsafe/failsafe_rxtx.c
+++ b/drivers/net/failsafe/failsafe_rxtx.c
@@ -28,39 +28,6 @@ fs_tx_unsafe(struct sub_device *sdev)
 		(sdev->state != DEV_STARTED);
 }
 
-void
-failsafe_set_burst_fn(struct rte_eth_dev *dev, int force_safe)
-{
-	struct sub_device *sdev;
-	uint8_t i;
-	int need_safe;
-	int safe_set;
-
-	need_safe = force_safe;
-	FOREACH_SUBDEV(sdev, i, dev)
-		need_safe |= fs_rx_unsafe(sdev);
-	safe_set = (dev->rx_pkt_burst == &failsafe_rx_burst);
-	if (need_safe && !safe_set) {
-		DEBUG("Using safe RX bursts%s",
-		      (force_safe ? " (forced)" : ""));
-		dev->rx_pkt_burst = &failsafe_rx_burst;
-	} else if (!need_safe && safe_set) {
-		DEBUG("Using fast RX bursts");
-		dev->rx_pkt_burst = &failsafe_rx_burst_fast;
-	}
-	need_safe = force_safe || fs_tx_unsafe(TX_SUBDEV(dev));
-	safe_set = (dev->tx_pkt_burst == &failsafe_tx_burst);
-	if (need_safe && !safe_set) {
-		DEBUG("Using safe TX bursts%s",
-		      (force_safe ? " (forced)" : ""));
-		dev->tx_pkt_burst = &failsafe_tx_burst;
-	} else if (!need_safe && safe_set) {
-		DEBUG("Using fast TX bursts");
-		dev->tx_pkt_burst = &failsafe_tx_burst_fast;
-	}
-	rte_wmb();
-}
-
 /*
  * Override source port in Rx packets.
  *
@@ -89,7 +56,7 @@ failsafe_rx_burst(void *queue,
 	rxq = queue;
 	sdev = rxq->sdev;
 	do {
-		if (fs_rx_unsafe(sdev)) {
+		if (unlikely(fs_rx_unsafe(sdev))) {
 			nb_rx = 0;
 			sdev = sdev->next;
 			continue;
@@ -108,34 +75,6 @@ failsafe_rx_burst(void *queue,
 	return nb_rx;
 }
 
-uint16_t
-failsafe_rx_burst_fast(void *queue,
-			 struct rte_mbuf **rx_pkts,
-			 uint16_t nb_pkts)
-{
-	struct sub_device *sdev;
-	struct rxq *rxq;
-	void *sub_rxq;
-	uint16_t nb_rx;
-
-	rxq = queue;
-	sdev = rxq->sdev;
-	do {
-		RTE_ASSERT(!fs_rx_unsafe(sdev));
-		sub_rxq = ETH(sdev)->data->rx_queues[rxq->qid];
-		FS_ATOMIC_P(rxq->refcnt[sdev->sid]);
-		nb_rx = ETH(sdev)->
-			rx_pkt_burst(sub_rxq, rx_pkts, nb_pkts);
-		FS_ATOMIC_V(rxq->refcnt[sdev->sid]);
-		sdev = sdev->next;
-	} while (nb_rx == 0 && sdev != rxq->sdev);
-	rxq->sdev = sdev;
-	if (nb_rx)
-		failsafe_rx_set_port(rx_pkts, nb_rx,
-				     rxq->priv->data->port_id);
-	return nb_rx;
-}
-
 uint16_t
 failsafe_tx_burst(void *queue,
 		  struct rte_mbuf **tx_pkts,
@@ -156,23 +95,3 @@ failsafe_tx_burst(void *queue,
 	FS_ATOMIC_V(txq->refcnt[sdev->sid]);
 	return nb_tx;
 }
-
-uint16_t
-failsafe_tx_burst_fast(void *queue,
-			 struct rte_mbuf **tx_pkts,
-			 uint16_t nb_pkts)
-{
-	struct sub_device *sdev;
-	struct txq *txq;
-	void *sub_txq;
-	uint16_t nb_tx;
-
-	txq = queue;
-	sdev = TX_SUBDEV(&rte_eth_devices[txq->priv->data->port_id]);
-	RTE_ASSERT(!fs_tx_unsafe(sdev));
-	sub_txq = ETH(sdev)->data->tx_queues[txq->qid];
-	FS_ATOMIC_P(txq->refcnt[sdev->sid]);
-	nb_tx = ETH(sdev)->tx_pkt_burst(sub_txq, tx_pkts, nb_pkts);
-	FS_ATOMIC_V(txq->refcnt[sdev->sid]);
-	return nb_tx;
-}
-- 
2.38.1