From bd85525efbf3ce382c12146ab89954e8bcdfd0be Mon Sep 17 00:00:00 2001 From: Qi Zhang Date: Tue, 18 Oct 2016 02:29:41 +0800 Subject: [PATCH] net/ixgbe: 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: c95584dc2b18 ("ixgbe: new vectorized functions for Rx/Tx") Signed-off-by: Qi Zhang Acked-by: Konstantin Ananyev --- drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c index ad8a9ffcfa..abbf2841f2 100644 --- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c +++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c @@ -343,6 +343,7 @@ _recv_raw_pkts_vec(struct ixgbe_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); @@ -351,8 +352,10 @@ _recv_raw_pkts_vec(struct ixgbe_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