Re: [PATCH] net/virtio: fix an incorrect behavior of device stop/start

On Fri, Sep 01, 2017 at 03:14:26PM +0800, Tiwei Bie wrote:

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On Tue, Aug 29, 2017 at 04:26:01PM +0800, Tiwei Bie wrote:

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After starting a device, the driver shouldn't deliver the
packets that already existed in the device before it is
started to the applications.

Otherwise? I'm assuming you fixed a real issue? If so, it'd be better
if you can add a bit info about the issue.

This patch fixes this issue

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by flushing the Rx queues when starting the device.

Fixes: a85786dc816f ("virtio: fix states handling during initialization")

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@@ -1737,6 +1737,12 @@ virtio_dev_start(struct rte_eth_dev *dev)

		}
	}

+	/* Flush the packets in Rx queues. */
+	for (i = 0; i < dev->data->nb_rx_queues; i++) {
+		rxvq = dev->data->rx_queues[i];
+		virtqueue_flush(rxvq->vq);
+	}
+

A little bit further down is a for loop going over rx queues calling
notify. Could we flush directly before the notify and save the
additional loop?

I saw there is also another `for' loop to dump the Rx queues.
And I think it makes the code more readable to flush the Rx
queues in a separate `for' loop too. Besides, this function
isn't performance critical. So I didn't combine them into one
`for' loop.

To me code is better readable when it is concise, so I'd still vote for
combining the loops if its logically equivalent.

On the other hand I think this should be fixed soon, so

Reviewed-by: Jens Freimann <redacted>

Thank you! :-)

It's not a big deal. I'd like to leave it up to the maintainers.
They can make the decision when applying the patch.

I agree with Jens here. We already have too many for loops in this
function. Let's not add yet another one. Besides that, the VIRTQUEU_DUMP
loop probably should also be removed and more it to the notify loop.

	--yliu