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net/virtio: fix read barriers on packed Tx cleanup

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Read barrier must be implied between reading descriptor flags
and descriptor id. Otherwise, in case of reordering, we could
read wrong descriptor id.

For the reference, similar barrier for split rings is the read
barrier between VIRTQUEUE_NUSED (reading the used->idx) and
the call to the virtio_xmit_cleanup().

Additionally removed double update of 'used_idx'. It's enough
to set it in the end of the loop.

Fixes: 892dc798fa9c ("net/virtio: implement Tx path for packed queues")
Cc: stable@dpdk.org

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
This commit is contained in:
Ilya Maximets 2019-01-24 19:59:00 +03:00 committed by Ferruh Yigit
parent e5ed1e5f38
commit 3eb50f0c79
1 changed files with 1 additions and 2 deletions
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3
drivers/net/virtio/virtio_rxtx.c
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@ -234,7 +234,7 @@ virtio_xmit_cleanup_packed(struct virtqueue *vq, int num)
used_idx = vq->vq_used_cons_idx;
while (num-- && desc_is_used(&desc[used_idx], vq)) {
used_idx = vq->vq_used_cons_idx;
virtio_rmb(vq->hw->weak_barriers);
id = desc[used_idx].id;
dxp = &vq->vq_descx[id];
vq->vq_used_cons_idx += dxp->ndescs;
@ -1940,7 +1940,6 @@ virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf **tx_pkts,
/* Positive value indicates it need free vring descriptors */
if (unlikely(need > 0)) {
virtio_rmb(hw->weak_barriers);
need = RTE_MIN(need, (int)nb_pkts);
virtio_xmit_cleanup_packed(vq, need);
need = slots - vq->vq_free_cnt;