From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: [PATCH v2 2/4] vhost: enforce desc flags and content read ordering Date: Wed, 19 Dec 2018 09:21:11 +0100 Message-ID: <20181219082113.24455-3-maxime.coquelin@redhat.com> References: <20181219082113.24455-1-maxime.coquelin@redhat.com> Cc: stable@dpdk.org, Maxime Coquelin To: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com, mst@redhat.com Return-path: In-Reply-To: <20181219082113.24455-1-maxime.coquelin@redhat.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" A read barrier is required to ensure that the ordering between descriptor's flags and content reads is enforced. 1. read flags = desc->flags if (flags & AVAIL_BIT) 2. read desc->id There is a control dependency between steps 1 and step 2. 2 could be speculatively executed before 1, which could result in 'id' to not be updated yet. Fixes: 2f3225a7d69b ("vhost: add vector filling support for packed ring") Cc: stable@dpdk.org Reported-by: Jason Wang Signed-off-by: Maxime Coquelin Acked-by: Ilya Maximets --- lib/librte_vhost/virtio_net.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index 7f37bbbed..a9b1bc55f 100644 --- a/lib/librte_vhost/virtio_net.c +++ b/lib/librte_vhost/virtio_net.c @@ -481,6 +481,12 @@ fill_vec_buf_packed(struct virtio_net *dev, struct vhost_virtqueue *vq, if (unlikely(!desc_is_avail(&descs[avail_idx], wrap_counter))) return -1; + /* + * The ordering between desc flags and desc + * content reads need to be enforced. + */ + rte_smp_rmb(); + *desc_count = 0; *len = 0; -- 2.17.2