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From: Kyle Larose <eomereadig@gmail.com>
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Subject: [dpdk-dev] vhost-net stops sending to virito pmd -- already fixed?
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Hi all,

I've been debugging an issue we see occasionally when under load. We have a
non-DPDK linux-bridge host sending to our guest via vhost-net. The guest is
running a DPDK 1.8 application using virtio PMDs.

The symptoms of the problem are that host interfaces report all packets
sent to the interface as being tx-discarded. The guest reports that no
packets are received.

Debugging the guest process, I found that the PMD thought that there were
no entries queued for reception:

$5 = {hw = 0x7f131fcfd600, mz = 0x7f1346200128, virtio_net_hdr_mz = 0x0,
mpool = 0x7f131ff8a0c0, queue_id = 0, port_id = 1 '\001', vq_ring_virt_mem
= 0x7f1339ebd000, vq_alignment = 4096, vq_ring_size = 12288, vq_ring_mem =
2081148928, vq_ring = {num = 256,
    desc = 0x7f1339ebd000, avail = 0x7f1339ebe000, used = 0x7f1339ebf000},
vq_free_cnt = 256, vq_nentries = 256, vq_queue_index = 0, vq_desc_head_idx
= 33, vq_desc_tail_idx = 32, vq_used_cons_idx = 37409, vq_avail_idx =
37409, virtio_net_hdr_mem = 0,
  packets = 67473953, bytes = 4049880780, errors = 0, vq_descx =
0x7f131fcf41d0}


(Basically, VIRTQUEUE_NUSED() was returning 0).

This makes me suspect that the guest and host fell out of sync.

Looking through the version tree for virtio_rxtx.c, I saw the following
commit:

http://dpdk.org/browse/dpdk/commit/lib/librte_pmd_virtio?id=8c09c20fb4cde76e53d87bd50acf2b441ecf6eb8

Does anybody know offhand if the issue fixed by that commit could be the
root cause of what I am seeing?

Thanks,

Kyle