From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [1/5] vhost: enforce avail index and desc read ordering Date: Tue, 11 Dec 2018 15:46:14 +0100 Message-ID: <151f312e-d238-d9ea-9a70-61b405703ce3@redhat.com> References: <20181205094957.1938-2-maxime.coquelin@redhat.com> <60168064-6a09-318b-1f62-78b3520e00f4@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: stable@dpdk.org To: Ilya Maximets , dev@dpdk.org, jfreimann@redhat.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com Return-path: In-Reply-To: <60168064-6a09-318b-1f62-78b3520e00f4@samsung.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 12/11/18 11:38 AM, Ilya Maximets wrote: > 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 >> Signed-off-by: Maxime Coquelin >> --- >> 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. Sure, I'll rework the commit message in the v2. > Otherwise, > Acked-by: Ilya Maximets Thanks, Maxime > >> 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); >>