Re: [REGRESSION] Commit 447cbe95ebb9 causes IOMMU DMA faults on macvlan/vlan with bnxt_en

[Eric Dumazet <edumazet@kernel.org>]

On 10/5/26 00:29, Michael Chan wrote:
> 
> I think skb->len is not updated with the padded length here.  So the
> HW will drop the packet seeing that the length is too short.  There is
> another skb_put_padto() that might work better?

+1 Exactly, thanks!

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c 
b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 
d7728d0c5b6e63ee72de9dea54426bb4c8b7a9fc..7ea27e81e88c5ca82a453b449982b791e8acc831 
100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -486,7 +486,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff 
*skb, struct net_device *dev)
         struct netdev_queue *txq;
         int i;
         dma_addr_t mapping;
-       unsigned int length, pad = 0;
+       unsigned int length;
         u32 len, free_size, vlan_tag_flags, cfa_action, flags;
         struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
         struct pci_dev *pdev = bp->pdev;
@@ -672,14 +672,12 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff 
*skb, struct net_device *dev)
         }

  normal_tx:
-       if (length < BNXT_MIN_PKT_SIZE) {
-               pad = BNXT_MIN_PKT_SIZE - length;
-               if (skb_pad(skb, pad))
-                       /* SKB already freed. */
-                       goto tx_kick_pending;
-               length = BNXT_MIN_PKT_SIZE;
+       if (skb_put_padto(skb, BNXT_MIN_PKT_SIZE)) {
+               /* SKB already freed. */
+               goto tx_kick_pending;
         }
-
+       length = skb->len;
+       len = skb_headlen(skb);
         mapping = dma_map_single(&pdev->dev, skb->data, len, 
DMA_TO_DEVICE);

         if (unlikely(dma_mapping_error(&pdev->dev, mapping)))
@@ -759,10 +757,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff 
*skb, struct net_device *dev)
                 txbd->tx_bd_len_flags_type = cpu_to_le32(flags);
         }

-       flags &= ~TX_BD_LEN;
-       txbd->tx_bd_len_flags_type =
-               cpu_to_le32(((len + pad) << TX_BD_LEN_SHIFT) | flags |
-                           TX_BD_FLAGS_PACKET_END);
+       txbd->tx_bd_len_flags_type |= cpu_to_le32(TX_BD_FLAGS_PACKET_END);

         netdev_tx_sent_queue(txq, skb->len);