[dpdk-dev] [PATCH] net/thunderx: check data offset alignment requirement

[Jerin Jacob]

nicvf HW expects the DMA address of the packet data to be
aligned with cache line size.

Packet data offset is a function of struct mbuf size,
mbuf private size and headroom. mbuf private size can
be changed from the application in pool creation, this
check detects HW alignment requirement constraint in pmd
start function.

Signed-off-by: Jerin Jacob <jerin.jacob at caviumnetworks.com>
---
 drivers/net/thunderx/nicvf_ethdev.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/thunderx/nicvf_ethdev.c b/drivers/net/thunderx/nicvf_ethdev.c
index 1060319..ad7b5d6 100644
--- a/drivers/net/thunderx/nicvf_ethdev.c
+++ b/drivers/net/thunderx/nicvf_ethdev.c
@@ -1410,7 +1410,7 @@ static int
 nicvf_vf_start(struct rte_eth_dev *dev, struct nicvf *nic, uint32_t rbdrsz)
 {
 	int ret;
-	uint16_t qidx;
+	uint16_t qidx, data_off;
 	uint32_t total_rxq_desc, nb_rbdr_desc, exp_buffs;
 	uint64_t mbuf_phys_off = 0;
 	struct nicvf_rxq *rxq;
@@ -1451,10 +1451,17 @@ nicvf_vf_start(struct rte_eth_dev *dev, struct nicvf *nic, uint32_t rbdrsz)
 				     nic->vf_id, qidx, rxq->pool->name);
 			return -ENOMEM;
 		}
-		rxq->mbuf_phys_off -= nicvf_mbuff_meta_length(mbuf);
-		rxq->mbuf_phys_off -= RTE_PKTMBUF_HEADROOM;
+		data_off = nicvf_mbuff_meta_length(mbuf);
+		data_off += RTE_PKTMBUF_HEADROOM;
 		rte_pktmbuf_free(mbuf);
 
+		if (data_off % RTE_CACHE_LINE_SIZE) {
+			PMD_INIT_LOG(ERR, "unaligned data_offset=%d delta=%d\n",
+				data_off, data_off % RTE_CACHE_LINE_SIZE);
+			return -EINVAL;
+		}
+		rxq->mbuf_phys_off -= data_off;
+
 		if (mbuf_phys_off == 0)
 			mbuf_phys_off = rxq->mbuf_phys_off;
 		if (mbuf_phys_off != rxq->mbuf_phys_off) {
-- 
2.5.5