From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id ADCF41BACE; Wed, 19 Dec 2018 09:21:27 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DE241C02835A; Wed, 19 Dec 2018 08:21:26 +0000 (UTC) Received: from localhost.localdomain (ovpn-112-26.ams2.redhat.com [10.36.112.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id BB22767E68; Wed, 19 Dec 2018 08:21:24 +0000 (UTC) From: Maxime Coquelin To: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com, mst@redhat.com Cc: stable@dpdk.org, Maxime Coquelin Date: Wed, 19 Dec 2018 09:21:10 +0100 Message-Id: <20181219082113.24455-2-maxime.coquelin@redhat.com> In-Reply-To: <20181219082113.24455-1-maxime.coquelin@redhat.com> References: <20181219082113.24455-1-maxime.coquelin@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 19 Dec 2018 08:21:26 +0000 (UTC) Subject: [dpdk-dev] [PATCH v2 1/4] vhost: enforce avail index and desc read ordering X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Dec 2018 08:21:28 -0000 A read barrier is required to ensure the ordering between available index and the descriptor reads is enforced. 1. read avail_head = avail->idx 2. read cur_idx = last_avail_idx if (cur_idx != avail_head) { 3. read idx = avail->ring[cur_idx] 4. read desc[idx] } There is a control dependency between step 1 and steps 3 & 4, 3 could be speculatively executed before 1, which could result in 'idx' to not being updated yet. Fixes: 4796ad63ba1f ("examples/vhost: import userspace vhost application") Cc: stable@dpdk.org Reported-by: Jason Wang Signed-off-by: Maxime Coquelin Acked-by: Ilya Maximets --- lib/librte_vhost/virtio_net.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index 8c657a101..7f37bbbed 100644 --- a/lib/librte_vhost/virtio_net.c +++ b/lib/librte_vhost/virtio_net.c @@ -752,6 +752,12 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]); avail_head = *((volatile uint16_t *)&vq->avail->idx); + /* + * The ordering between avail index and + * desc reads needs to be enforced. + */ + rte_smp_rmb(); + for (pkt_idx = 0; pkt_idx < count; pkt_idx++) { uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen; uint16_t nr_vec = 0; @@ -1334,6 +1340,12 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, if (free_entries == 0) return 0; + /* + * The ordering between avail index and + * desc reads needs to be enforced. + */ + rte_smp_rmb(); + VHOST_LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__); count = RTE_MIN(count, MAX_PKT_BURST); -- 2.17.2