Re: [PATCH net-next v9 13/15] net: lan966x: add PCIe FDMA XDP support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] net: lan966x: missing RX stats update for packets consumed by XDP
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commit c200183575cbdbcd07153d60fe18b2c59693c034
Author: Daniel Machon <daniel.machon@microchip.com>

net: lan966x: add PCIe FDMA XDP support

Add XDP support for the PCIe FDMA path. The implementation operates on
contiguous ATU-mapped buffers with memcpy-based XDP_TX, unlike the
platform path which uses page_pool.

> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
> index 758554c951c52..949994874ed96 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
[ ... ]
> @@ -349,8 +466,17 @@ static int lan966x_fdma_pci_napi_poll(struct napi_struct *napi, int weight)
>  			 */
>  			fdma_dcb_advance(fdma);
>  			continue;
> +		case FDMA_TX:
> +			fdma_dcb_advance(fdma);
> +			continue;
> +		case FDMA_DROP:
> +			fdma_dcb_advance(fdma);
> +			continue;

[Severity: Medium]
Will this result in missing RX statistics for packets handled by XDP?

Because the loop continues immediately on FDMA_TX and FDMA_DROP verdicts, it
skips lan966x_fdma_pci_rx_get_frame() entirely. Since
lan966x_fdma_pci_rx_get_frame() is the only place where rx_packets and
rx_bytes are updated, does this mean packets dropped or transmitted by XDP
are not counted as received on the interface?

For example, lan966x_fdma_pci_rx_get_frame() updates these stats:

        skb->dev->stats.rx_bytes += skb->len;
        skb->dev->stats.rx_packets++;

Could these statistics be updated when the packets are processed in
lan966x_fdma_pci_napi_poll(), even if they are consumed by XDP?

>  		}
> -		skb = lan966x_fdma_pci_rx_get_frame(rx, src_port);
> +		skb = lan966x_fdma_pci_rx_get_frame(rx,
> +						    src_port,
> +						    data,
> +						    data_len);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260928-lan966x-pci-fdma-v9-0-a17caf60f89a@microchip.com?part=13