[dpdk-dev] [PATCH v2 3/3] net/af_xdp: fix maximum MTU value

[dpdk-dev] [PATCH v2 3/3] net/af_xdp: fix maximum MTU value

[Ciara Loftus]

The maximum MTU for af_xdp zero copy is equal to the page size less the
frame overhead introduced by AF_XDP (XDP HR = 256) and DPDK (frame headroom
= 320). The patch updates this value to reflect this.

This change also makes it possible to remove unneeded constants for both
zero-copy and copy mode.

Fixes: d8a210774e1d ("net/af_xdp: support unaligned umem chunks")
Cc: stable@dpdk.org

Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 1e98cd44f..75f037c3e 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -59,13 +59,6 @@ static int af_xdp_logtype;
 
 #define ETH_AF_XDP_FRAME_SIZE		2048
 #define ETH_AF_XDP_NUM_BUFFERS		4096
-#ifdef XDP_UMEM_UNALIGNED_CHUNK_FLAG
-#define ETH_AF_XDP_MBUF_OVERHEAD	128 /* sizeof(struct rte_mbuf) */
-#define ETH_AF_XDP_DATA_HEADROOM \
-	(ETH_AF_XDP_MBUF_OVERHEAD + RTE_PKTMBUF_HEADROOM)
-#else
-#define ETH_AF_XDP_DATA_HEADROOM	0
-#endif
 #define ETH_AF_XDP_DFLT_NUM_DESCS	XSK_RING_CONS__DEFAULT_NUM_DESCS
 #define ETH_AF_XDP_DFLT_START_QUEUE_IDX	0
 #define ETH_AF_XDP_DFLT_QUEUE_COUNT	1
@@ -602,7 +595,14 @@ eth_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
 	dev_info->max_tx_queues = internals->queue_cnt;
 
 	dev_info->min_mtu = RTE_ETHER_MIN_MTU;
-	dev_info->max_mtu = ETH_AF_XDP_FRAME_SIZE - ETH_AF_XDP_DATA_HEADROOM;
+#if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
+	dev_info->max_mtu = getpagesize() -
+				sizeof(struct rte_mempool_objhdr) -
+				sizeof(struct rte_mbuf) -
+				RTE_PKTMBUF_HEADROOM - XDP_PACKET_HEADROOM;
+#else
+	dev_info->max_mtu = ETH_AF_XDP_FRAME_SIZE;
+#endif
 
 	dev_info->default_rxportconf.nb_queues = 1;
 	dev_info->default_txportconf.nb_queues = 1;
@@ -804,7 +804,7 @@ xsk_umem_info *xdp_umem_configure(struct pmd_internals *internals,
 		.fill_size = ETH_AF_XDP_DFLT_NUM_DESCS,
 		.comp_size = ETH_AF_XDP_DFLT_NUM_DESCS,
 		.frame_size = ETH_AF_XDP_FRAME_SIZE,
-		.frame_headroom = ETH_AF_XDP_DATA_HEADROOM };
+		.frame_headroom = 0 };
 	char ring_name[RTE_RING_NAMESIZE];
 	char mz_name[RTE_MEMZONE_NAMESIZE];
 	int ret;
@@ -829,8 +829,7 @@ xsk_umem_info *xdp_umem_configure(struct pmd_internals *internals,
 
 	for (i = 0; i < ETH_AF_XDP_NUM_BUFFERS; i++)
 		rte_ring_enqueue(umem->buf_ring,
-				 (void *)(i * ETH_AF_XDP_FRAME_SIZE +
-					  ETH_AF_XDP_DATA_HEADROOM));
+				 (void *)(i * ETH_AF_XDP_FRAME_SIZE));
 
 	snprintf(mz_name, sizeof(mz_name), "af_xdp_umem_%s_%u",
 		       internals->if_name, rxq->xsk_queue_idx);
@@ -939,7 +938,7 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
 	/* Now get the space available for data in the mbuf */
 	buf_size = rte_pktmbuf_data_room_size(mb_pool) -
 		RTE_PKTMBUF_HEADROOM;
-	data_size = ETH_AF_XDP_FRAME_SIZE - ETH_AF_XDP_DATA_HEADROOM;
+	data_size = ETH_AF_XDP_FRAME_SIZE;
 
 	if (data_size > buf_size) {
 		AF_XDP_LOG(ERR, "%s: %d bytes will not fit in mbuf (%d bytes)\n",
-- 
2.17.1