Re: [net-next v8 07/10] net: bnxt: Implement software USO

[Eric Dumazet]

On Thu, Apr 2, 2026 at 5:36 PM Joe Damato <joe@xxxxxxx> wrote:
>
> Implement bnxt_sw_udp_gso_xmit() using the core tso_dma_map API and
> the pre-allocated TX inline buffer for per-segment headers.
>
> The xmit path:
> 1. Calls tso_start() to initialize TSO state
> 2. Stack-allocates a tso_dma_map and calls tso_dma_map_init() to
>    DMA-map the linear payload and all frags upfront.
> 3. For each segment:
>    - Copies and patches headers via tso_build_hdr() into the
>      pre-allocated tx_inline_buf (DMA-synced per segment)
>    - Counts payload BDs via tso_dma_map_count()
>    - Emits long BD (header) + ext BD + payload BDs
>    - Payload BDs use tso_dma_map_next() which yields (dma_addr,
>      chunk_len, mapping_len) tuples.
>
> Header BDs set dma_unmap_len=0 since the inline buffer is pre-allocated
> and unmapped only at ring teardown.
>
> Completion state is updated by calling tso_dma_map_completion_save() for
> the last segment.
>
> Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Joe Damato <joe@xxxxxxx>
> ---
>


> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> index 6b38b84924e0..fe50576ae525 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> @@ -11,6 +11,8 @@
>  #ifndef BNXT_H
>  #define BNXT_H
>
> +#include <net/tso.h>
> +
>  #define DRV_MODULE_NAME                "bnxt_en"
>
>  /* DO NOT CHANGE DRV_VER_* defines
> @@ -899,6 +901,7 @@ struct bnxt_sw_tx_bd {
>                 u16                     rx_prod;
>                 u16                     txts_prod;
>         };
> +       struct tso_dma_map_completion_state sw_gso_cstate;
>  };
>
>  #define BNXT_SW_GSO_MID                1
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> index b296769ee4fe..7a7d40e36cea 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> @@ -19,11 +19,213 @@
>  #include "bnxt.h"
>  #include "bnxt_gso.h"
>
> +static u32 bnxt_sw_gso_lhint(unsigned int len)
> +{
> +       if (len <= 512)
> +               return TX_BD_FLAGS_LHINT_512_AND_SMALLER;
> +       else if (len <= 1023)
> +               return TX_BD_FLAGS_LHINT_512_TO_1023;
> +       else if (len <= 2047)
> +               return TX_BD_FLAGS_LHINT_1024_TO_2047;
> +       else
> +               return TX_BD_FLAGS_LHINT_2048_AND_LARGER;
> +}
> +
>  netdev_tx_t bnxt_sw_udp_gso_xmit(struct bnxt *bp,
>                                  struct bnxt_tx_ring_info *txr,
>                                  struct netdev_queue *txq,
>                                  struct sk_buff *skb)
>  {
> +       unsigned int last_unmap_len __maybe_unused = 0;
> +       dma_addr_t last_unmap_addr __maybe_unused = 0;
> +       struct bnxt_sw_tx_bd *last_unmap_buf = NULL;
> +       unsigned int hdr_len, mss, num_segs;
> +       struct pci_dev *pdev = bp->pdev;
> +       unsigned int total_payload;
> +       struct tso_dma_map map;
> +       u32 vlan_tag_flags = 0;
> +       int i, bds_needed;
> +       struct tso_t tso;
> +       u16 cfa_action;
> +       u16 prod;
> +
> +       hdr_len = tso_start(skb, &tso);

Orthogonal to your patch:

It seems that tso_start() users do not really check if hdr_len could
be bigger than
their expectations ( TSO_HEADER_SIZE for many of them).

Presumably these drivers should have an ndo_features_check() to detect
this and fallback to GSO.

I can send a series to fix this.