Date:   Fri, 22 Nov 2019 05:31:19 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Julio Faracco <jcfaracco@...il.com>
Cc:     netdev@...r.kernel.org, dnmendes76@...il.com,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] drivers: net: virtio_net: Implement a
 dev_watchdog handler

On Thu, Nov 21, 2019 at 10:36:36PM -0300, Julio Faracco wrote:
> Driver virtio_net is not handling error events for TX provided by
> dev_watchdog. This event is reached when transmission queue is having
> problems to transmit packets. This could happen for any reason. To
> enable it, driver should have .ndo_tx_timeout implemented.
> 
> This commit brings back virtnet_reset method to recover TX queues from a
> error state. That function is called by schedule_work method and it puts
> the reset function into work queue.
> 
> As the error cause is unknown at this moment, it would be better to
> reset all queues.
> 
> Signed-off-by: Julio Faracco <jcfaracco@...il.com>
> Signed-off-by: Daiane Mendes <dnmendes76@...il.com>
> Cc: Jason Wang <jasowang@...hat.com>
> ---
> v1-v2: Tag `net-next` was included to indentify where patch would be
> applied.
> ---
>  drivers/net/virtio_net.c | 95 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 94 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4d7d5434cc5d..31890d77eaf2 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -75,6 +75,7 @@ struct virtnet_sq_stats {
>  	u64 xdp_tx;
>  	u64 xdp_tx_drops;
>  	u64 kicks;
> +	u64 tx_timeouts;
>  };
>  
>  struct virtnet_rq_stats {
> @@ -98,6 +99,7 @@ static const struct virtnet_stat_desc virtnet_sq_stats_desc[] = {
>  	{ "xdp_tx",		VIRTNET_SQ_STAT(xdp_tx) },
>  	{ "xdp_tx_drops",	VIRTNET_SQ_STAT(xdp_tx_drops) },
>  	{ "kicks",		VIRTNET_SQ_STAT(kicks) },
> +	{ "tx_timeouts",	VIRTNET_SQ_STAT(tx_timeouts) },
>  };
>  
>  static const struct virtnet_stat_desc virtnet_rq_stats_desc[] = {
> @@ -211,6 +213,9 @@ struct virtnet_info {
>  	/* Work struct for config space updates */
>  	struct work_struct config_work;
>  
> +	/* Work struct for resetting the virtio-net driver. */
> +	struct work_struct reset_work;
> +
>  	/* Does the affinity hint is set for virtqueues? */
>  	bool affinity_hint_set;
>  
> @@ -1721,7 +1726,7 @@ static void virtnet_stats(struct net_device *dev,
>  	int i;
>  
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
> -		u64 tpackets, tbytes, rpackets, rbytes, rdrops;
> +		u64 tpackets, tbytes, terrors, rpackets, rbytes, rdrops;
>  		struct receive_queue *rq = &vi->rq[i];
>  		struct send_queue *sq = &vi->sq[i];
>  
> @@ -1729,6 +1734,7 @@ static void virtnet_stats(struct net_device *dev,
>  			start = u64_stats_fetch_begin_irq(&sq->stats.syncp);
>  			tpackets = sq->stats.packets;
>  			tbytes   = sq->stats.bytes;
> +			terrors  = sq->stats.tx_timeouts;
>  		} while (u64_stats_fetch_retry_irq(&sq->stats.syncp, start));
>  
>  		do {
> @@ -1743,6 +1749,7 @@ static void virtnet_stats(struct net_device *dev,
>  		tot->rx_bytes   += rbytes;
>  		tot->tx_bytes   += tbytes;
>  		tot->rx_dropped += rdrops;
> +		tot->tx_errors  += terrors;
>  	}
>  
>  	tot->tx_dropped = dev->stats.tx_dropped;
> @@ -2578,6 +2585,33 @@ static int virtnet_set_features(struct net_device *dev,
>  	return 0;
>  }
>  
> +static void virtnet_tx_timeout(struct net_device *dev)
> +{
> +	struct virtnet_info *vi = netdev_priv(dev);
> +	u32 i;
> +
> +	netdev_warn(dev, "TX timeout stats:\n");
> +	/* find the stopped queue the same way dev_watchdog() does */
> +	for (i = 0; i < vi->curr_queue_pairs; i++) {
> +		struct send_queue *sq = &vi->sq[i];
> +
> +		if (!netif_xmit_stopped(netdev_get_tx_queue(dev, i))) {
> +			netdev_warn(dev, " Available send queue: %d, sq: %s, vq: %d, name: %s\n",
> +				    i, sq->name, sq->vq->index, sq->vq->name);

What does this mean?

> +			continue;
> +		}
> +
> +		u64_stats_update_begin(&sq->stats.syncp);
> +		sq->stats.tx_timeouts++;
> +		u64_stats_update_end(&sq->stats.syncp);
> +
> +		netdev_warn(dev, " Unavailable send queue: %d, sq: %s, vq: %d, name: %s\n",
> +			    i, sq->name, sq->vq->index, sq->vq->name);
> +	}

Can we make the warning less cryptic?
I wonder why don't we get the sq from timeout directly?
Would seem cleaner.

> +
> +	schedule_work(&vi->reset_work);
> +}
> +
>  static const struct net_device_ops virtnet_netdev = {
>  	.ndo_open            = virtnet_open,
>  	.ndo_stop   	     = virtnet_close,
> @@ -2593,6 +2627,7 @@ static const struct net_device_ops virtnet_netdev = {
>  	.ndo_features_check	= passthru_features_check,
>  	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
>  	.ndo_set_features	= virtnet_set_features,
> +	.ndo_tx_timeout		= virtnet_tx_timeout,
>  };
>  
>  static void virtnet_config_changed_work(struct work_struct *work)
> @@ -2982,6 +3017,62 @@ static int virtnet_validate(struct virtio_device *vdev)
>  	return 0;
>  }
>  
> +static void _remove_vq_common(struct virtnet_info *vi)
> +{
> +	vi->vdev->config->reset(vi->vdev);
> +
> +	/* Free unused buffers in both send and recv, if any. */
> +	free_unused_bufs(vi);
> +
> +	_free_receive_bufs(vi);
> +
> +	free_receive_page_frags(vi);
> +
> +	virtnet_del_vqs(vi);
> +}
> +
> +static int _virtnet_reset(struct virtnet_info *vi)
> +{
> +	struct virtio_device *vdev = vi->vdev;
> +	int ret;
> +
> +	virtio_config_disable(vdev);
> +	vdev->failed = vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_FAILED;
> +
> +	virtnet_freeze_down(vdev);
> +	_remove_vq_common(vi);
> +
> +	virtio_add_status(vdev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
> +	virtio_add_status(vdev, VIRTIO_CONFIG_S_DRIVER);
> +
> +	ret = virtio_finalize_features(vdev);
> +	if (ret)
> +		goto err;
> +
> +	ret = virtnet_restore_up(vdev);
> +	if (ret)
> +		goto err;
> +
> +	ret = _virtnet_set_queues(vi, vi->curr_queue_pairs);
> +	if (ret)
> +		goto err;
> +
> +	virtio_add_status(vdev, VIRTIO_CONFIG_S_DRIVER_OK);
> +	virtio_config_enable(vdev);


Is this enough? E.g. all RX mode programming has been lost.



> +	return 0;
> +err:
> +	virtio_add_status(vdev, VIRTIO_CONFIG_S_FAILED);
> +	return ret;
> +}
> +
> +static void virtnet_reset(struct work_struct *work)
> +{
> +	struct virtnet_info *vi =
> +		container_of(work, struct virtnet_info, reset_work);
> +
> +	_virtnet_reset(vi);
> +}
> +
>  static int virtnet_probe(struct virtio_device *vdev)
>  {
>  	int i, err = -ENOMEM;
> @@ -3011,6 +3102,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	dev->netdev_ops = &virtnet_netdev;
>  	dev->features = NETIF_F_HIGHDMA;
>  
> +	dev->watchdog_timeo = 5 * HZ;
>  	dev->ethtool_ops = &virtnet_ethtool_ops;
>  	SET_NETDEV_DEV(dev, &vdev->dev);
>

Is there a way to make this tuneable from ethtool?
  
> @@ -3068,6 +3160,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	vdev->priv = vi;
>  
>  	INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> +	INIT_WORK(&vi->reset_work, virtnet_reset);
>  
>  	/* If we can receive ANY GSO packets, we must allocate large ones. */
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> -- 
> 2.17.1

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