[dpdk-stable] patch 'net/ixgbe: fix out of order Rx read' has been queued to stable release 16.07.2

[Yuanhan Liu]

Hi,

FYI, your patch has been queued to stable release 16.07.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable
yet. It will be pushed if I get no objections before 11/06/16.
So please shout if anyone has objections.

Thanks.

	--yliu

---
>From 92704c3dfb390939ca6b4831853062fa375938bd Mon Sep 17 00:00:00 2001
From: Qi Zhang <qi.z.zhang at intel.com>
Date: Tue, 18 Oct 2016 02:29:41 +0800
Subject: [PATCH] net/ixgbe: fix out of order Rx read

[ upstream commit bd85525efbf3ce382c12146ab89954e8bcdfd0be ]

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 <qi.z.zhang at intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
---
 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 1c4fd7c..7fb155a 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
@@ -305,6 +305,7 @@ _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);
@@ -313,8 +314,10 @@ _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  */
-- 
1.9.0