Re: [PATCH net-next] virtio_net: set link state down when virtqueue is broken

在 2021/5/28 下午6:58, wangyunjian 写道:

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-----Original Message-----

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From: Yunjian Wang <redacted>

The NIC can't receive/send packets if a rx/tx virtqueue is broken.
However, the link state of the NIC is still normal. As a result, the
user cannot detect the NIC exception.

Doesn't we have:

         /* This should not happen! */
          if (unlikely(err)) {
                  dev->stats.tx_fifo_errors++;
                  if (net_ratelimit())
                          dev_warn(&dev->dev,
                                   "Unexpected TXQ (%d) queue
failure: %d\n",
                                   qnum, err);
                  dev->stats.tx_dropped++;
                  dev_kfree_skb_any(skb);
                  return NETDEV_TX_OK;
          }

Which should be sufficient?

There may be other reasons for this error, e.g -ENOSPC(no free desc).

This should not happen unless the device or driver is buggy. We always reserved sufficient slots:

        if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
                netif_stop_subqueue(dev, qnum);
...

And if rx virtqueue is broken, there is no error statistics.

Feel free to add one if it's necessary.

Let's leave the policy decision (link down) to userspace.

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The driver can set the link state down when the virtqueue is broken.
If the state is down, the user can switch over to another NIC.

Note that, we probably need the watchdog for virtio-net in order to be a
complete solution.

Yes, I can think of is that the virtqueue's broken exception is detected on watchdog.
Is there anything else that needs to be done?

Basically, it's all about TX stall which watchdog tries to catch. Broken vq is only one of the possible reason.

Thanks

Thanks

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Thanks