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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-dev] [1/5] vhost: enforce avail index and desc read ordering
Date: Tue, 11 Dec 2018 13:38:46 +0300	[thread overview]
Message-ID: <60168064-6a09-318b-1f62-78b3520e00f4@samsung.com> (raw)
In-Reply-To: <20181205094957.1938-2-maxime.coquelin@redhat.com>

On 05.12.2018 12:49, Maxime Coquelin wrote:
> A read barrier is required to ensure the ordering between
> available index and the descriptor reads is enforced.
> 
> Fixes: 4796ad63ba1f ("examples/vhost: import userspace vhost application")
> 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 | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 

I'd like to have a bit more details about a bad scenario in a commit
message because it's not an obvious change at a first glance.

Otherwise,
Acked-by: Ilya Maximets <i.maximets@samsung.com>


> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 5e1a1a727..f11ebb54f 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -791,6 +791,12 @@ 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;
> @@ -1373,6 +1379,12 @@ 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);
> 

  parent reply	other threads:[~2018-12-11 10:38 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-05  9:49 [dpdk-dev] [PATCH 0/5] vhost: add missing barriers, remove useless volatiles Maxime Coquelin
2018-12-05  9:49 ` [dpdk-dev] [PATCH 1/5] vhost: enforce avail index and desc read ordering Maxime Coquelin
     [not found]   ` <CGME20181205113041eucas1p1943b9c13af2fb5b736ba4906b59a9cd5@eucas1p1.samsung.com>
2018-12-05 11:30     ` [dpdk-dev] [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 [this message]
2018-12-11 14:46       ` Maxime Coquelin
2018-12-05  9:49 ` [dpdk-dev] [PATCH 2/5] vhost: enforce desc flags and content " Maxime Coquelin
     [not found]   ` <CGME20181205133332eucas1p195b3864ed146403e314d7004d27be285@eucas1p1.samsung.com>
2018-12-05 13:33     ` [dpdk-dev] [2/5] " Ilya Maximets
2018-12-06  4:24       ` Jason Wang
2018-12-06 11:34         ` Ilya Maximets
2018-12-05  9:49 ` [dpdk-dev] [PATCH 3/5] vhost: prefetch descriptor after the read barrier Maxime Coquelin
2018-12-05  9:49 ` [dpdk-dev] [PATCH 4/5] vhost: remove useless prefetch for packed ring descriptor Maxime Coquelin
2018-12-05  9:49 ` [dpdk-dev] [PATCH 5/5] vhost: remove useless casts to volatile Maxime Coquelin
     [not found]   ` <CGME20181205135231eucas1p1c89281f6525a0fedab4a2fc0d2e21393@eucas1p1.samsung.com>
2018-12-05 13:52     ` [dpdk-dev] [5/5] " Ilya Maximets
2018-12-06 16:59       ` Maxime Coquelin
2018-12-07 11:16         ` Ilya Maximets

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