From: Ilya Maximets <i.maximets@samsung.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>,
dev@dpdk.org, jfreimann@redhat.com, tiwei.bie@intel.com,
zhihong.wang@intel.com, jasowang@redhat.com
Cc: stable@dpdk.org
Subject: Re: [dpdk-stable] [2/5] vhost: enforce desc flags and content read ordering
Date: Wed, 5 Dec 2018 16:33:31 +0300 [thread overview]
Message-ID: <16a4b2fd-c701-7822-3215-62e431e3f339@samsung.com> (raw)
In-Reply-To: <20181205094957.1938-3-maxime.coquelin@redhat.com>
On 05.12.2018 12:49, Maxime Coquelin wrote:
> A read barrier is required to ensure that the ordering between
> descriptor's flags and content reads is enforced.
>
> 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>
> ---
> 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 f11ebb54f..68b72e7a5 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -520,6 +520,12 @@ 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();
> +
Same here. 'desc_is_avail' reads and uses the flags. i.e.
no way for reordering,
Writes must be ordered on the virtio side by the write barrier.
This means that if flags are updated (desc_is_avail() == true)
than the whole descriptor already updated and the data is written.
No need to have any read barriers here.
> *desc_count = 0;
> *len = 0;
>
>
next prev parent reply other threads:[~2018-12-05 13:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20181205094957.1938-1-maxime.coquelin@redhat.com>
2018-12-05 9:49 ` [dpdk-stable] [PATCH 1/5] vhost: enforce avail index and desc " Maxime Coquelin
[not found] ` <CGME20181205113041eucas1p1943b9c13af2fb5b736ba4906b59a9cd5@eucas1p1.samsung.com>
2018-12-05 11:30 ` [dpdk-stable] [1/5] " Ilya Maximets
2018-12-06 4:17 ` Jason Wang
2018-12-06 12:48 ` Ilya Maximets
2018-12-06 13:25 ` Jason Wang
2018-12-06 13:48 ` Michael S. Tsirkin
2018-12-07 14:58 ` Ilya Maximets
2018-12-07 15:44 ` Michael S. Tsirkin
[not found] ` <CGME20181211103848eucas1p10c270ca8997fea8a2f55c2d94d02baea@eucas1p1.samsung.com>
2018-12-11 10:38 ` Ilya Maximets
2018-12-11 14:46 ` Maxime Coquelin
2018-12-05 9:49 ` [dpdk-stable] [PATCH 2/5] vhost: enforce desc flags and content " Maxime Coquelin
[not found] ` <CGME20181205133332eucas1p195b3864ed146403e314d7004d27be285@eucas1p1.samsung.com>
2018-12-05 13:33 ` Ilya Maximets [this message]
2018-12-06 4:24 ` [dpdk-stable] [2/5] " Jason Wang
2018-12-06 11:34 ` Ilya Maximets
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