Re: [PATCH net,v2] ethernet: ionic: Fix DMA mapping tests

[Brett Creeley <bcreeley@amd.com>]

On 6/17/2025 11:57 AM, Thomas Fourier wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> Removing wrappers around `dma_map_XXX()` to prevent collision between
> 0 as a valid address and 0 as an error code.
> 
> Fixes: ac8813c0ab7d ("ionic: convert Rx queue buffers to use page_pool")
> Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
> ---
> Another solution is to remove the wrappers altogether so that it doesn't
> call multiple times the `dma_mapping_error()`.  This also makes the code
> more similar to other calls of the DMA mapping API (even if wrappers
> around the DMA API are quite common, checking the return code of mapping
> in the wrapper does not seem to be common).

This is one solution, but this requires adding extra goto labels and 
pulling the print(s) outside of the helper functions. It also increases 
the size of the diff from a fixes patch that could be a few lines.

I would prefer returning DMA_MAPPING_ERROR from the 
ionic_tx_map_single() and ionic_tx_map_frag() on failure and checking 
for that in the callers.

Thanks,

Brett

> 
> Thomas
> 
>   .../net/ethernet/pensando/ionic/ionic_txrx.c  | 70 ++++++-------------
>   1 file changed, 22 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> index 2ac59564ded1..1905790d0c4d 100644
> --- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> +++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> @@ -12,12 +12,7 @@
>   #include "ionic_lif.h"
>   #include "ionic_txrx.h"
> 
> -static dma_addr_t ionic_tx_map_single(struct ionic_queue *q,
> -                                     void *data, size_t len);
> 
> -static dma_addr_t ionic_tx_map_frag(struct ionic_queue *q,
> -                                   const skb_frag_t *frag,
> -                                   size_t offset, size_t len);
> 
>   static void ionic_tx_desc_unmap_bufs(struct ionic_queue *q,
>                                       struct ionic_tx_desc_info *desc_info);
> @@ -320,9 +315,9 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
>                  dma_sync_single_for_device(q->dev, dma_addr,
>                                             len, DMA_TO_DEVICE);
>          } else /* XDP_REDIRECT */ {
> -               dma_addr = ionic_tx_map_single(q, frame->data, len);
> -               if (!dma_addr)
> -                       return -EIO;
> +               dma_addr = dma_map_single(q->dev, frame->data, len, DMA_TO_DEVICE);
> +               if (dma_mapping_error(q->dev, dma_addr))
> +                       goto dma_err;
>          }
> 
>          buf_info->dma_addr = dma_addr;
> @@ -355,11 +350,12 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
>                                                             skb_frag_size(frag),
>                                                             DMA_TO_DEVICE);
>                          } else {
> -                               dma_addr = ionic_tx_map_frag(q, frag, 0,
> -                                                            skb_frag_size(frag));
> +                               dma_addr = skb_frag_dma_map(q->dev, frag, 0,
> +                                                           skb_frag_size(frag),
> +                                                           DMA_TO_DEVICE);
>                                  if (dma_mapping_error(q->dev, dma_addr)) {
>                                          ionic_tx_desc_unmap_bufs(q, desc_info);
> -                                       return -EIO;
> +                                       goto dma_err;
>                                  }
>                          }
>                          bi->dma_addr = dma_addr;
> @@ -388,6 +384,12 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
>          ionic_txq_post(q, ring_doorbell);
> 
>          return 0;
> +
> +dma_err:
> +       net_warn_ratelimited("%s: DMA map failed on %s!\n",
> +                            dev_name(q->dev), q->name);
> +       q_to_tx_stats(q)->dma_map_err++;
> +       return -EIO;
>   }
> 
>   int ionic_xdp_xmit(struct net_device *netdev, int n,
> @@ -1072,38 +1074,6 @@ int ionic_txrx_napi(struct napi_struct *napi, int budget)
>          return rx_work_done;
>   }
> 
> -static dma_addr_t ionic_tx_map_single(struct ionic_queue *q,
> -                                     void *data, size_t len)
> -{
> -       struct device *dev = q->dev;
> -       dma_addr_t dma_addr;
> -
> -       dma_addr = dma_map_single(dev, data, len, DMA_TO_DEVICE);
> -       if (unlikely(dma_mapping_error(dev, dma_addr))) {
> -               net_warn_ratelimited("%s: DMA single map failed on %s!\n",
> -                                    dev_name(dev), q->name);
> -               q_to_tx_stats(q)->dma_map_err++;
> -               return 0;
> -       }
> -       return dma_addr;
> -}
> -
> -static dma_addr_t ionic_tx_map_frag(struct ionic_queue *q,
> -                                   const skb_frag_t *frag,
> -                                   size_t offset, size_t len)
> -{
> -       struct device *dev = q->dev;
> -       dma_addr_t dma_addr;
> -
> -       dma_addr = skb_frag_dma_map(dev, frag, offset, len, DMA_TO_DEVICE);
> -       if (unlikely(dma_mapping_error(dev, dma_addr))) {
> -               net_warn_ratelimited("%s: DMA frag map failed on %s!\n",
> -                                    dev_name(dev), q->name);
> -               q_to_tx_stats(q)->dma_map_err++;
> -               return 0;
> -       }
> -       return dma_addr;
> -}
> 
>   static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
>                              struct ionic_tx_desc_info *desc_info)
> @@ -1115,9 +1085,9 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
>          skb_frag_t *frag;
>          int frag_idx;
> 
> -       dma_addr = ionic_tx_map_single(q, skb->data, skb_headlen(skb));
> -       if (!dma_addr)
> -               return -EIO;
> +       dma_addr = dma_map_single(q->dev, skb->data, skb_headlen(skb), DMA_TO_DEVICE);
> +       if (dma_mapping_error(q->dev, dma_addr))
> +               goto dma_early_fail;
>          buf_info->dma_addr = dma_addr;
>          buf_info->len = skb_headlen(skb);
>          buf_info++;
> @@ -1125,8 +1095,8 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
>          frag = skb_shinfo(skb)->frags;
>          nfrags = skb_shinfo(skb)->nr_frags;
>          for (frag_idx = 0; frag_idx < nfrags; frag_idx++, frag++) {
> -               dma_addr = ionic_tx_map_frag(q, frag, 0, skb_frag_size(frag));
> -               if (!dma_addr)
> +               dma_addr = skb_frag_dma_map(q->dev, frag, 0, skb_frag_size(frag), DMA_TO_DEVICE);
> +               if (dma_mapping_error(q->dev, dma_addr))
>                          goto dma_fail;
>                  buf_info->dma_addr = dma_addr;
>                  buf_info->len = skb_frag_size(frag);
> @@ -1147,6 +1117,10 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
>          }
>          dma_unmap_single(dev, desc_info->bufs[0].dma_addr,
>                           desc_info->bufs[0].len, DMA_TO_DEVICE);
> +dma_early_fail:
> +       net_warn_ratelimited("%s: DMA map failed on %s!\n",
> +                            dev_name(dev), q->name);
> +       q_to_tx_stats(q)->dma_map_err++;
>          return -EIO;
>   }
> 
> --
> 2.43.0
>