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 <jcfara...@gmail.com>
Signed-off-by: Daiane Mendes <dnmende...@gmail.com>
Cc: Jason Wang <jasow...@redhat.com>
---
 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);
+                       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);
+       }
+
+       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);
+       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);
 
@@ -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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