net/thunderx: add compile-time checks

The thunderx PMD is sensitive to the layout of the mbuf on
the RX path. Add in some compile-time checks to make sure the mbuf layout
assumptions are valid, and to provide hints to anyone changing the mbuf
where things may need to be updated.

Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>

diff --git a/drivers/net/thunderx/nicvf_ethdev.c b/drivers/net/thunderx/nicvf_ethdev.c
index 2152029..3421415 100644 (file)
--- a/drivers/net/thunderx/nicvf_ethdev.c
+++ b/drivers/net/thunderx/nicvf_ethdev.c
@@ -1239,6 +1239,13 @@ nicvf_rxq_mbuf_setup(struct nicvf_rxq *rxq)
        struct rte_mbuf mb_def;
 
        RTE_BUILD_BUG_ON(sizeof(union mbuf_initializer) != 8);
+       RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, data_off) % 8 != 0);
+       RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, refcnt) -
+                               offsetof(struct rte_mbuf, data_off) != 2);
+       RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, nb_segs) -
+                               offsetof(struct rte_mbuf, data_off) != 4);
+       RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, port) -
+                               offsetof(struct rte_mbuf, data_off) != 6);
        mb_def.nb_segs = 1;
        mb_def.data_off = RTE_PKTMBUF_HEADROOM;
        mb_def.port = rxq->port_id;