[dpdk-dev] [PATCH 1/4] net/ixgbe: add compile-time checks to vector driver

[Bruce Richardson]

The vector PMD is very sensitive to the layout of the mbuf, especially 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: Bruce Richardson <bruce.richardson at intel.com>
---
 drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
index 795ee33..83a96b5 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
@@ -87,6 +87,8 @@ ixgbe_rxq_rearm(struct ixgbe_rx_queue *rxq)
 		mb1 = rxep[1].mbuf;
 
 		/* load buf_addr(lo 64bit) and buf_physaddr(hi 64bit) */
+		RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, buf_physaddr) !=
+				offsetof(struct rte_mbuf, buf_addr) + 8);
 		vaddr0 = _mm_loadu_si128((__m128i *)&(mb0->buf_addr));
 		vaddr1 = _mm_loadu_si128((__m128i *)&(mb1->buf_addr));
 
@@ -234,6 +236,11 @@ desc_to_olflags_v(__m128i descs[4], __m128i mbuf_init, uint8_t vlan_flags,
 
 #endif /* RTE_MACHINE_CPUFLAG_SSE4_2 */
 
+	/* write the rearm data and the olflags in one write */
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, ol_flags) !=
+			offsetof(struct rte_mbuf, rearm_data) + 8);
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, rearm_data) !=
+			RTE_ALIGN(offsetof(struct rte_mbuf, rearm_data), 16));
 	_mm_store_si128((__m128i *)&rx_pkts[0]->rearm_data, rearm0);
 	_mm_store_si128((__m128i *)&rx_pkts[1]->rearm_data, rearm1);
 	_mm_store_si128((__m128i *)&rx_pkts[2]->rearm_data, rearm2);
@@ -266,6 +273,15 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 				-rxq->crc_len, /* sub crc on pkt_len */
 				0, 0            /* ignore pkt_type field */
 			);
+	/*
+	 * compile-time check the above crc_adjust layout is correct.
+	 * NOTE: the first field (lowest address) is given last in set_epi16
+	 * call above.
+	 */
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, pkt_len) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 4);
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, data_len) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 8);
 	__m128i dd_check, eop_check;
 	__m128i mbuf_init;
 	uint8_t vlan_flags;
@@ -312,6 +328,19 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 		0xFF, 0xFF,  /* skip 32 bit pkt_type */
 		0xFF, 0xFF
 		);
+	/*
+	 * Compile-time verify the shuffle mask
+	 * NOTE: some field positions already verified above, but duplicated
+	 * here for completeness in case of future modifications.
+	 */
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, pkt_len) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 4);
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, data_len) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 8);
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, vlan_tci) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 10);
+	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, hash) !=
+			offsetof(struct rte_mbuf, rx_descriptor_fields1) + 12);
 
 	mbuf_init = _mm_set_epi64x(0, rxq->mbuf_initializer);
 
-- 
2.9.3