Re: [PATCH net-next v8 6/9] eth: bnxt: adjust the fill level of agg queues with larger buffers

Paolo Abeni
2026-01-13T10:27:56Z

On 1/9/26 12:28 PM, Pavel Begunkov wrote:
> From: Jakub Kicinski <kuba@kernel.org>
>
> The driver tries to provision more agg buffers than header buffers
> since multiple agg segments can reuse the same header. The calculation
> / heuristic tries to provide enough pages for 65k of data for each header
> (or 4 frags per header if the result is too big). This calculation is
> currently global to the adapter. If we increase the buffer sizes 8x
> we don't want 8x the amount of memory sitting on the rings.
> Luckily we don't have to fill the rings completely, adjust
> the fill level dynamically in case particular queue has buffers
> larger than the global size.
>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> [pavel: rebase on top of agg_size_fac, assert agg_size_fac]
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
> drivers/net/ethernet/broadcom/bnxt/bnxt.c | 28 +++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 8f42885a7c86..137e348d2b9c 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -3816,16 +3816,34 @@ static void bnxt_free_rx_rings(struct bnxt *bp)
> }
> }
>
> +static int bnxt_rx_agg_ring_fill_level(struct bnxt *bp,
> + struct bnxt_rx_ring_info *rxr)
> +{
> + /* User may have chosen larger than default rx_page_size,
> + * we keep the ring sizes uniform and also want uniform amount
> + * of bytes consumed per ring, so cap how much of the rings we fill.
> + */
> + int fill_level = bp->rx_agg_ring_size;
> +
> + if (rxr->rx_page_size > BNXT_RX_PAGE_SIZE)
> + fill_level /= rxr->rx_page_size / BNXT_RX_PAGE_SIZE;

According to the check in bnxt_alloc_rx_page_pool() it's theoretically
possible for `rxr->rx_page_size / BNXT_RX_PAGE_SIZE` being zero. If so
the above would crash.

Side note: this looks like something AI review could/should catch. The
fact it didn't makes me think I'm missing something...

/P