From: Maxime Coquelin <maxime.coquelin@redhat.com>
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 <maxime.coquelin@redhat.com>
Subject: [dpdk-stable] [PATCH v2 2/4] vhost: enforce desc flags and content read ordering
Date: Wed, 19 Dec 2018 09:21:11 +0100 [thread overview]
Message-ID: <20181219082113.24455-3-maxime.coquelin@redhat.com> (raw)
In-Reply-To: <20181219082113.24455-1-maxime.coquelin@redhat.com>
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 <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
---
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
next prev parent reply other threads:[~2018-12-19 8:21 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 8:21 [dpdk-stable] [PATCH v2 0/4] vhost: add missing barriers, move prefetching Maxime Coquelin
2018-12-19 8:21 ` [dpdk-stable] [PATCH v2 1/4] vhost: enforce avail index and desc read ordering Maxime Coquelin
2018-12-19 15:47 ` Michael S. Tsirkin
2018-12-19 15:50 ` Maxime Coquelin
2018-12-19 8:21 ` Maxime Coquelin [this message]
2018-12-19 8:21 ` [dpdk-stable] [PATCH v2 3/4] vhost: prefetch descriptor after the read barrier Maxime Coquelin
2018-12-19 8:21 ` [dpdk-stable] [PATCH v2 4/4] vhost: remove useless prefetch for packed ring descriptor Maxime Coquelin
2018-12-19 15:49 ` Michael S. Tsirkin
2018-12-19 15:50 ` [dpdk-stable] [PATCH v2 0/4] vhost: add missing barriers, move prefetching Michael S. Tsirkin
2018-12-19 16:28 ` Ilya Maximets
2018-12-20 4:39 ` Tiwei Bie
2018-12-20 18:19 ` Maxime Coquelin
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