From ff6edd388603a8331217b13bb002cfd0c0e471b3 Mon Sep 17 00:00:00 2001 From: Qi Zhang Date: Tue, 18 Oct 2016 02:29:40 +0800 Subject: [PATCH] net/i40e: fix out of order Rx read In vPMD, when we load Rx desc with _mm_loadu_si128, the volatile modifier will be cast away, allowing the compiler to reorder the load instructions. The Rx recv function's correctness is relying on these load instructions following a strict sequence, reading the descriptors in reverse order, so we add compiler barrier to prevent compiler reorder. Fixes: 9ed94e5bb04e ("i40e: add vector Rx") Signed-off-by: Qi Zhang Acked-by: Konstantin Ananyev --- drivers/net/i40e/i40e_rxtx_vec_sse.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/i40e/i40e_rxtx_vec_sse.c b/drivers/net/i40e/i40e_rxtx_vec_sse.c index 3607312ce6..7c84a41aba 100644 --- a/drivers/net/i40e/i40e_rxtx_vec_sse.c +++ b/drivers/net/i40e/i40e_rxtx_vec_sse.c @@ -306,6 +306,7 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts, /* Read desc statuses backwards to avoid race condition */ /* A.1 load 4 pkts desc */ descs[3] = _mm_loadu_si128((__m128i *)(rxdp + 3)); + rte_compiler_barrier(); /* B.2 copy 2 mbuf point into rx_pkts */ _mm_storeu_si128((__m128i *)&rx_pkts[pos], mbp1); @@ -314,8 +315,10 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts, mbp2 = _mm_loadu_si128((__m128i *)&sw_ring[pos+2]); descs[2] = _mm_loadu_si128((__m128i *)(rxdp + 2)); + rte_compiler_barrier(); /* B.1 load 2 mbuf point */ descs[1] = _mm_loadu_si128((__m128i *)(rxdp + 1)); + rte_compiler_barrier(); descs[0] = _mm_loadu_si128((__m128i *)(rxdp)); /* B.2 copy 2 mbuf point into rx_pkts */ -- 2.20.1