Patch "net: hns3: fix tx timeout issue" has been added to the 6.5-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: hns3: fix tx timeout issue

to the 6.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-hns3-fix-tx-timeout-issue.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit dabe1b0e70aa270baa870856a49fa9b677037a5e
Author: Jian Shen <shenjian15@xxxxxxxxxx>
Date:   Wed Sep 6 15:20:12 2023 +0800

    net: hns3: fix tx timeout issue
    
    [ Upstream commit 61a1deacc3d4fd3d57d7fda4d935f7f7503e8440 ]
    
    Currently, the driver knocks the ring doorbell before updating
    the ring->last_to_use in tx flow. if the hardware transmiting
    packet and napi poll scheduling are fast enough, it may get
    the old ring->last_to_use in drivers' napi poll.
    In this case, the driver will think the tx is not completed, and
    return directly without clear the flag __QUEUE_STATE_STACK_XOFF,
    which may cause tx timeout.
    
    Fixes: 20d06ca2679c ("net: hns3: optimize the tx clean process")
    Signed-off-by: Jian Shen <shenjian15@xxxxxxxxxx>
    Signed-off-by: Jijie Shao <shaojijie@xxxxxxxxxx>
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index b7b51e56b0308..71772213b4448 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -2102,8 +2102,12 @@ static void hns3_tx_doorbell(struct hns3_enet_ring *ring, int num,
 	 */
 	if (test_bit(HNS3_NIC_STATE_TX_PUSH_ENABLE, &priv->state) && num &&
 	    !ring->pending_buf && num <= HNS3_MAX_PUSH_BD_NUM && doorbell) {
+		/* This smp_store_release() pairs with smp_load_aquire() in
+		 * hns3_nic_reclaim_desc(). Ensure that the BD valid bit
+		 * is updated.
+		 */
+		smp_store_release(&ring->last_to_use, ring->next_to_use);
 		hns3_tx_push_bd(ring, num);
-		WRITE_ONCE(ring->last_to_use, ring->next_to_use);
 		return;
 	}
 
@@ -2114,6 +2118,11 @@ static void hns3_tx_doorbell(struct hns3_enet_ring *ring, int num,
 		return;
 	}
 
+	/* This smp_store_release() pairs with smp_load_aquire() in
+	 * hns3_nic_reclaim_desc(). Ensure that the BD valid bit is updated.
+	 */
+	smp_store_release(&ring->last_to_use, ring->next_to_use);
+
 	if (ring->tqp->mem_base)
 		hns3_tx_mem_doorbell(ring);
 	else
@@ -2121,7 +2130,6 @@ static void hns3_tx_doorbell(struct hns3_enet_ring *ring, int num,
 		       ring->tqp->io_base + HNS3_RING_TX_RING_TAIL_REG);
 
 	ring->pending_buf = 0;
-	WRITE_ONCE(ring->last_to_use, ring->next_to_use);
 }
 
 static void hns3_tsyn(struct net_device *netdev, struct sk_buff *skb,
@@ -3562,9 +3570,8 @@ static void hns3_reuse_buffer(struct hns3_enet_ring *ring, int i)
 static bool hns3_nic_reclaim_desc(struct hns3_enet_ring *ring,
 				  int *bytes, int *pkts, int budget)
 {
-	/* pair with ring->last_to_use update in hns3_tx_doorbell(),
-	 * smp_store_release() is not used in hns3_tx_doorbell() because
-	 * the doorbell operation already have the needed barrier operation.
+	/* This smp_load_acquire() pairs with smp_store_release() in
+	 * hns3_tx_doorbell().
 	 */
 	int ltu = smp_load_acquire(&ring->last_to_use);
 	int ntc = ring->next_to_clean;