From 778602fe570a138224de94a38eca3ce2e344138c Mon Sep 17 00:00:00 2001 From: Ruifeng Wang Date: Wed, 15 Sep 2021 16:33:38 +0800 Subject: [PATCH] net/i40e: fix risk in descriptor read in NEON Rx Rx descriptor is 16B/32B in size. If the DD bit is set, it indicates that the rest of the descriptor words have valid values. Hence, the word containing DD bit must be read first before reading the rest of the descriptor words. In NEON vector PMD, vector load loads two contiguous 8B of descriptor data into vector register. Given vector load ensures no 16B atomicity, read of the word that includes DD field could be reordered after read of other words. In this case, some words could contain invalid data. Read barrier is added after read of qword1 that includes DD field. And qword0 is reloaded to update vector register. This ensures that the fetched data is correct. Testpmd single core test on N1SDP/ThunderX2 showed no performance drop. Fixes: ae0eb310f253 ("net/i40e: implement vector PMD for ARM") Cc: stable@dpdk.org Signed-off-by: Ruifeng Wang Reviewed-by: Honnappa Nagarahalli --- drivers/net/i40e/i40e_rxtx_vec_neon.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/net/i40e/i40e_rxtx_vec_neon.c b/drivers/net/i40e/i40e_rxtx_vec_neon.c index b2683fda60..71191c7cc8 100644 --- a/drivers/net/i40e/i40e_rxtx_vec_neon.c +++ b/drivers/net/i40e/i40e_rxtx_vec_neon.c @@ -286,6 +286,14 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *__rte_restrict rxq, descs[1] = vld1q_u64((uint64_t *)(rxdp + 1)); descs[0] = vld1q_u64((uint64_t *)(rxdp)); + /* Use acquire fence to order loads of descriptor qwords */ + rte_atomic_thread_fence(__ATOMIC_ACQUIRE); + /* A.2 reload qword0 to make it ordered after qword1 load */ + descs[3] = vld1q_lane_u64((uint64_t *)(rxdp + 3), descs[3], 0); + descs[2] = vld1q_lane_u64((uint64_t *)(rxdp + 2), descs[2], 0); + descs[1] = vld1q_lane_u64((uint64_t *)(rxdp + 1), descs[1], 0); + descs[0] = vld1q_lane_u64((uint64_t *)(rxdp), descs[0], 0); + /* B.1 load 4 mbuf point */ mbp1 = vld1q_u64((uint64_t *)&sw_ring[pos]); mbp2 = vld1q_u64((uint64_t *)&sw_ring[pos + 2]); -- 2.20.1