Re: [PATCH v2 06/10] net/virtio: fix queue setup consistency

[Tiwei Bie <tiwei.bie@intel.com>]

Hi Maxime and Olivier:

On Thu, Sep 07, 2017 at 02:13:43PM +0200, Olivier Matz wrote:
[...]
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index 8eee3ff80..c7888f103 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -1737,6 +1737,19 @@ virtio_dev_start(struct rte_eth_dev *dev)
>  	struct virtnet_rx *rxvq;
>  	struct virtnet_tx *txvq __rte_unused;
>  	struct virtio_hw *hw = dev->data->dev_private;
> +	int ret;
> +
> +	/* Finish the initialization of the queues */
> +	for (i = 0; i < dev->data->nb_rx_queues; i++) {
> +		ret = virtio_dev_rx_queue_setup_finish(dev, i);
> +		if (ret < 0)
> +			return ret;
> +	}

I'm trying to fix an issue [1] reported by Antonio. And during
the debugging, I found that vector Rx of virtio PMD has been
broken (when doing port stop/start) since below two patches were
applied:

25bf7a0b0936 ("vhost: make error handling consistent in Rx path")
   -- needed on the Tx side (testpmd/vhost-pmd in below test)
efc83a1e7fc3 ("net/virtio: fix queue setup consistency")
   -- needed on the Rx side (testpmd/virtio-user in below test)

Below are the steps to reproduce the issue:

#0. Checkout the commit

# 25bf7a0b0936 was applied after efc83a1e7fc3
git checkout 25bf7a0b0936

(There is another vector Rx bug caused by rxq flushing on the
 HEAD. So it's better to checkout the old commit first.)

#1. Apply below patch to disable mergeable Rx, and build DPDK

diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
index 2039bc5..d45ffa5 100644
--- a/drivers/net/virtio/virtio_ethdev.h
+++ b/drivers/net/virtio/virtio_ethdev.h
@@ -65,7 +65,6 @@
 	 1u << VIRTIO_NET_F_CSUM	  |	\
 	 1u << VIRTIO_NET_F_HOST_TSO4	  |	\
 	 1u << VIRTIO_NET_F_HOST_TSO6	  |	\
-	 1u << VIRTIO_NET_F_MRG_RXBUF	  |	\
 	 1u << VIRTIO_NET_F_MTU	| \
 	 1u << VIRTIO_RING_F_INDIRECT_DESC |    \
 	 1ULL << VIRTIO_F_VERSION_1       |	\

#2. Launch testpmd/vhost-pmd:

./x86_64-native-linuxapp-gcc/app/testpmd -l 1,2 \
	--socket-mem 1024,1024 \
	--file-prefix=vhost \
	--no-pci \
	--vdev=net_vhost0,iface=/tmp/socket-0,queues=1 \
	-- \
	--port-topology=chained \
	-i \
	--nb-cores=1

#3. Launch testpmd/virtio-user:

./x86_64-native-linuxapp-gcc/app/testpmd -l 5,6 \
	--socket-mem 1024,1024 \
	--file-prefix=virtio-user \
	--no-pci \
	--vdev=net_virtio_user0,path=/tmp/socket-0 \
	-- \
	--port-topology=chained \
	-i \
	--nb-cores=1 \
	--disable-hw-vlan \
	--txqflags=0xf01

#4. In testpmd/virtio-user run below commands:

testpmd> set fwd rxonly
testpmd> start

#5. In testpmd/vhost-pmd run below commands:

testpmd> set burst 1
testpmd> set fwd rxonly
testpmd> start tx_first 1
testpmd> stop

#6. In testpmd/virtio-user run below commands:

testpmd> stop
testpmd> port stop all
testpmd> port start all
testpmd> start

#7. In testpmd/vhost-pmd run below commands:

testpmd> set fwd txonly
testpmd> start

#8. In testpmd/virtio-user run below commands:

testpmd> show port stats all

And you will see that there is no traffic any more after
receiving a few hundred packets.

[1] http://dpdk.org/ml/archives/dev/2017-December/082983.html

Best regards,
Tiwei Bie