Re: [PATCH v7 2/2] net/af_xdp: Refactor af_xdp_tx_zc

[Maryam Tahhan <mtahhan@redhat.com>]

Hi Ariel

Have you had a chance to test this? I'm currently getting a segfault 
with testpmd

testpmd>
Thread 4 "dpdk-worker0" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff4e00400 (LWP 3768882)]
0x0000000000b57b44 in eth_af_xdp_tx ()

Thanks
Maryam

On 01/02/2025 10:03, Ariel Otilibili wrote:
> Both legs of the loop share the same logic: the common parts are about
> reserving and filling both address and length into the description.
>
> This is moved into reserve_and_fill().
>
> Bugzilla ID: 1440
> Suggested-by: Maryam Tahhan <mtahhan@redhat.com>
> Signed-off-by: Ariel Otilibili <ariel.otilibili@6wind.com>
> ---
>   drivers/net/af_xdp/rte_eth_af_xdp.c | 62 ++++++++++++++++-------------
>   1 file changed, 34 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
> index 092bcb73aa0a..840a12dbf508 100644
> --- a/drivers/net/af_xdp/rte_eth_af_xdp.c
> +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
> @@ -536,6 +536,31 @@ kick_tx(struct pkt_tx_queue *txq, struct xsk_ring_cons *cq)
>   		}
>   }
>   
> +static inline struct xdp_desc *
> +reserve_and_fill(struct pkt_tx_queue *txq, struct rte_mbuf *mbuf,
> +		 struct xsk_umem_info *umem)
> +{
> +	struct xdp_desc *desc = NULL;
> +	uint32_t *idx_tx = NULL;
> +	uint64_t addr, offset;
> +
> +	if (!xsk_ring_prod__reserve(&txq->tx, 1, idx_tx))
> +		goto out;
> +
> +	desc = xsk_ring_prod__tx_desc(&txq->tx, *idx_tx);
> +	desc->len = mbuf->pkt_len;
> +
> +	addr = (uint64_t)mbuf - (uint64_t)umem->buffer
> +		- umem->mb_pool->header_size;
> +	offset = rte_pktmbuf_mtod(mbuf, uint64_t) - (uint64_t)mbuf
> +		+ umem->mb_pool->header_size;
> +	offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> +	desc->addr = addr | offset;
> +
> +out:
> +	return desc;
> +}
> +
>   #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
>   static uint16_t
>   af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> @@ -545,10 +570,8 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   	struct rte_mbuf *mbuf;
>   	unsigned long tx_bytes = 0;
>   	int i;
> -	uint32_t idx_tx;
>   	uint16_t count = 0;
>   	struct xdp_desc *desc;
> -	uint64_t addr, offset;
>   	struct xsk_ring_cons *cq = &txq->pair->cq;
>   	uint32_t free_thresh = cq->size >> 1;
>   
> @@ -559,21 +582,12 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   		mbuf = bufs[i];
>   
>   		if (mbuf->pool == umem->mb_pool) {
> -			if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
> +			if (!(desc = reserve_and_fill(txq, mbuf, umem))) {
>   				kick_tx(txq, cq);
> -				if (!xsk_ring_prod__reserve(&txq->tx, 1,
> -							    &idx_tx))
> +				if (!(desc = reserve_and_fill(txq, mbuf, umem)))
>   					goto out;
>   			}
> -			desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
> -			desc->len = mbuf->pkt_len;
> -			addr = (uint64_t)mbuf - (uint64_t)umem->buffer -
> -					umem->mb_pool->header_size;
> -			offset = rte_pktmbuf_mtod(mbuf, uint64_t) -
> -					(uint64_t)mbuf +
> -					umem->mb_pool->header_size;
> -			offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> -			desc->addr = addr | offset;
> +
>   			tx_bytes += desc->len;
>   			count++;
>   		} else {
> @@ -584,26 +598,18 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   			if (local_mbuf == NULL)
>   				goto out;
>   
> -			if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
> +			if (!(desc = reserve_and_fill(txq, local_mbuf, umem))) {
>   				rte_pktmbuf_free(local_mbuf);
>   				goto out;
>   			}
>   
> -			desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
> -			desc->len = mbuf->pkt_len;
> -
> -			addr = (uint64_t)local_mbuf - (uint64_t)umem->buffer -
> -					umem->mb_pool->header_size;
> -			offset = rte_pktmbuf_mtod(local_mbuf, uint64_t) -
> -					(uint64_t)local_mbuf +
> -					umem->mb_pool->header_size;
> -			pkt = xsk_umem__get_data(umem->buffer, addr + offset);
> -			offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> -			desc->addr = addr | offset;
> +			pkt = xsk_umem__get_data(umem->buffer,
> +						 (desc->addr & ~0xFFF)
> +						 + (desc->addr & 0xFFF));
>   			rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> -					desc->len);
> -			tx_bytes += desc->len;
> +				   desc->len);
>   			rte_pktmbuf_free(mbuf);
> +			tx_bytes += desc->len;
>   			count++;
>   		}
>   	}