Re: [PATCH net v2] net: ti: icssg-prueth: fix XDP_TX from the AF_XDP zero-copy RX path

[Meghana Malladi <m-malladi@ti.com>]

Few nitpicks,

On 6/23/26 16:52, David Carlier wrote:
> On XDP_TX from the zero-copy RX path, emac_run_xdp() converts the xsk
> buffer via xdp_convert_zc_to_xdp_frame(), which clones the data into a
> fresh MEM_TYPE_PAGE_ORDER0 page that is not DMA mapped. Transmitting it
> as PRUETH_TX_BUFF_TYPE_XDP_TX derives the DMA address with
> page_pool_get_dma_addr(), reading an uninitialized page->dma_addr, so
> the device DMAs from a bogus address (corrupt TX, or an IOMMU fault).
> 
> Pick the TX buffer type from the frame's memory type: keep
> PRUETH_TX_BUFF_TYPE_XDP_TX for page_pool frames and use
> PRUETH_TX_BUFF_TYPE_XDP_NDO for the cloned zero-copy frame, which is then
> DMA mapped through the NDO path and unmapped on completion.
> 
> While at it, fix the page_pool XDP_TX completion path. A
> PRUETH_TX_BUFF_TYPE_XDP_TX frame carries a page_pool-owned DMA mapping
> (established against rx_chn->dma_dev), yet prueth_xmit_free()
> unconditionally calls dma_unmap_single() on it with tx_chn->dma_dev,
> tearing down a mapping the driver does not own; xdp_return_frame()
> already recycles the page back to the pool. Tag such frames with a
> dedicated PRUETH_SWDATA_XDPF_TX type so the completion path skips the
> unmap, the same way PRUETH_SWDATA_XSK buffers are handled.
> 
> Fixes: 7a64bb388df3 ("net: ti: icssg-prueth: Add AF_XDP zero copy for RX")
> Fixes: 62aa3246f462 ("net: ti: icssg-prueth: Add XDP support")
> Cc: stable@vger.kernel.org
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
> v2:
>   - fold in the page_pool XDP_TX completion-path unmap fix raised by
>     Meghana Malladi: tag page_pool TX frames with PRUETH_SWDATA_XDPF_TX
>     so prueth_xmit_free() skips dma_unmap_single() on a pool-owned
>     mapping; xdp_return_frame() already recycles the page.
>   - add Fixes: 62aa3246f462 for that path.
>   - no change to the original zero-copy fix.
> v1: https://lore.kernel.org/netdev/20260620213756.87499-1-devnexen@gmail.com
>   drivers/net/ethernet/ti/icssg/icssg_common.c | 20 +++++++++++++++++---
>   drivers/net/ethernet/ti/icssg/icssg_prueth.h |  1 +
>   2 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
> index 82ddef9c17d5..96c8bf5ef671 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_common.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
> @@ -185,7 +185,7 @@ void prueth_xmit_free(struct prueth_tx_chn *tx_chn,
>   	first_desc = desc;
>   	next_desc = first_desc;
>   	swdata = cppi5_hdesc_get_swdata(first_desc);
> -	if (swdata->type == PRUETH_SWDATA_XSK)
> +	if (swdata->type == PRUETH_SWDATA_XSK || swdata->type == PRUETH_SWDATA_XDPF_TX)

line length crosses 80 characters

>   		goto free_pool;
>   
>   	cppi5_hdesc_get_obuf(first_desc, &buf_dma, &buf_dma_len);
> @@ -259,6 +259,7 @@ int emac_tx_complete_packets(struct prueth_emac *emac, int chn,
>   			napi_consume_skb(skb, budget);
>   			break;
>   		case PRUETH_SWDATA_XDPF:
> +		case PRUETH_SWDATA_XDPF_TX:
>   			xdpf = swdata->data.xdpf;
>   			dev_sw_netstats_tx_add(ndev, 1, xdpf->len);
>   			total_bytes += xdpf->len;
> @@ -769,7 +770,8 @@ u32 emac_xmit_xdp_frame(struct prueth_emac *emac,
>   	k3_udma_glue_tx_dma_to_cppi5_addr(tx_chn->tx_chn, &buf_dma);
>   	cppi5_hdesc_attach_buf(first_desc, buf_dma, xdpf->len, buf_dma, xdpf->len);
>   	swdata = cppi5_hdesc_get_swdata(first_desc);
> -	swdata->type = PRUETH_SWDATA_XDPF;
> +	swdata->type = buff_type == PRUETH_TX_BUFF_TYPE_XDP_TX ?
> +		PRUETH_SWDATA_XDPF_TX : PRUETH_SWDATA_XDPF;

Use braces for the condition please

>   	swdata->data.xdpf = xdpf;
>   
>   	/* Report BQL before sending the packet */
> @@ -804,6 +806,7 @@ EXPORT_SYMBOL_GPL(emac_xmit_xdp_frame);
>    */
>   static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, u32 *len)
>   {
> +	enum prueth_tx_buff_type tx_buff_type;
>   	struct net_device *ndev = emac->ndev;
>   	struct netdev_queue *netif_txq;
>   	int cpu = smp_processor_id();
> @@ -826,11 +829,21 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, u32 *len
>   			goto drop;
>   		}
>   
> +		/* In AF_XDP zero-copy mode xdp_convert_buff_to_frame()
> +		 * clones the xsk buffer into a fresh MEM_TYPE_PAGE_ORDER0
> +		 * page that is not DMA mapped. Such a frame must be mapped
> +		 * via the NDO path; only a page pool-backed frame already
> +		 * carries a usable page_pool DMA address.
> +		 */
> +		tx_buff_type = xdpf->mem_type == MEM_TYPE_PAGE_POOL ?
> +				PRUETH_TX_BUFF_TYPE_XDP_TX :
> +				PRUETH_TX_BUFF_TYPE_XDP_NDO;
> +
>   		q_idx = cpu % emac->tx_ch_num;
>   		netif_txq = netdev_get_tx_queue(ndev, q_idx);
>   		__netif_tx_lock(netif_txq, cpu);
>   		result = emac_xmit_xdp_frame(emac, xdpf, q_idx,
> -					     PRUETH_TX_BUFF_TYPE_XDP_TX);
> +					     tx_buff_type);
>   		__netif_tx_unlock(netif_txq);
>   		if (result == ICSSG_XDP_CONSUMED) {
>   			ndev->stats.tx_dropped++;
> @@ -1395,6 +1408,7 @@ void prueth_tx_cleanup(void *data, dma_addr_t desc_dma)
>   		dev_kfree_skb_any(skb);
>   		break;
>   	case PRUETH_SWDATA_XDPF:
> +	case PRUETH_SWDATA_XDPF_TX:
>   		xdpf = swdata->data.xdpf;
>   		xdp_return_frame(xdpf);
>   		break;
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.h b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> index df93d15c5b78..00bb760d68a9 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> @@ -153,6 +153,7 @@ enum prueth_swdata_type {
>   	PRUETH_SWDATA_CMD,
>   	PRUETH_SWDATA_XDPF,
>   	PRUETH_SWDATA_XSK,
> +	PRUETH_SWDATA_XDPF_TX,
>   };
>   
>   enum prueth_tx_buff_type {

Reviewed-by: Meghana Malladi <m-malladi@ti.com>