Subject: Re: [PATCH V3 net-next 1/2] virtio-net: convert rx mode setting to use workqueue

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 24 May 2023 05:15:03 -0400

On Wed, May 24, 2023 at 04:18:41PM +0800, Jason Wang wrote:
> This patch convert rx mode setting to be done in a workqueue, this is
> a must for allow to sleep when waiting for the cvq command to
> response since current code is executed under addr spin lock.
> 
> Signed-off-by: Jason Wang <[email-masked]>
> ---
> Changes since V1:
> - use RTNL to synchronize rx mode worker
> ---
>  drivers/net/virtio_net.c | 55 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 56ca1d270304..5d2f1da4eaa0 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -265,6 +265,12 @@ struct virtnet_info {
>  	/* Work struct for config space updates */
>  	struct work_struct config_work;
>  
> +	/* Work struct for config rx mode */

With a bit less abbreviation maybe? setting rx mode?

> +	struct work_struct rx_mode_work;
> +
> +	/* Is rx mode work enabled? */

Ugh not a great comment.

> +	bool rx_mode_work_enabled;
> +

>  	/* Does the affinity hint is set for virtqueues? */
>  	bool affinity_hint_set;
>  
> @@ -388,6 +394,20 @@ static void disable_delayed_refill(struct virtnet_info *vi)
>  	spin_unlock_bh(&vi->refill_lock);
>  }
>  
> +static void enable_rx_mode_work(struct virtnet_info *vi)
> +{
> +	rtnl_lock();
> +	vi->rx_mode_work_enabled = true;
> +	rtnl_unlock();
> +}
> +
> +static void disable_rx_mode_work(struct virtnet_info *vi)
> +{
> +	rtnl_lock();
> +	vi->rx_mode_work_enabled = false;
> +	rtnl_unlock();
> +}
> +
>  static void virtqueue_napi_schedule(struct napi_struct *napi,
>  				    struct virtqueue *vq)
>  {
> @@ -2341,9 +2361,11 @@ static int virtnet_close(struct net_device *dev)
>  	return 0;
>  }
>  
> -static void virtnet_set_rx_mode(struct net_device *dev)
> +static void virtnet_rx_mode_work(struct work_struct *work)
>  {
> -	struct virtnet_info *vi = netdev_priv(dev);
> +	struct virtnet_info *vi =
> +		container_of(work, struct virtnet_info, rx_mode_work);
> +	struct net_device *dev = vi->dev;
>  	struct scatterlist sg[2];
>  	struct virtio_net_ctrl_mac *mac_data;
>  	struct netdev_hw_addr *ha;
> @@ -2356,6 +2378,8 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
>  		return;
>  
> +	rtnl_lock();
> +
>  	vi->ctrl->promisc = ((dev->flags & IFF_PROMISC) != 0);
>  	vi->ctrl->allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
>  
> @@ -2373,14 +2397,19 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  		dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
>  			 vi->ctrl->allmulti ? "en" : "dis");
>  
> +	netif_addr_lock_bh(dev);
> +
>  	uc_count = netdev_uc_count(dev);
>  	mc_count = netdev_mc_count(dev);
>  	/* MAC filter - use one buffer for both lists */
>  	buf = kzalloc(((uc_count + mc_count) * ETH_ALEN) +
>  		      (2 * sizeof(mac_data->entries)), GFP_ATOMIC);
>  	mac_data = buf;
> -	if (!buf)
> +	if (!buf) {
> +		netif_addr_unlock_bh(dev);
> +		rtnl_unlock();
>  		return;
> +	}
>  
>  	sg_init_table(sg, 2);
>  
> @@ -2401,6 +2430,8 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  	netdev_for_each_mc_addr(ha, dev)
>  		memcpy(&mac_data->macs[i++][0], ha->addr, ETH_ALEN);
>  
> +	netif_addr_unlock_bh(dev);
> +
>  	sg_set_buf(&sg[1], mac_data,
>  		   sizeof(mac_data->entries) + (mc_count * ETH_ALEN));
>  
> @@ -2408,9 +2439,19 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  				  VIRTIO_NET_CTRL_MAC_TABLE_SET, sg))
>  		dev_warn(&dev->dev, "Failed to set MAC filter table.\n");
>  
> +	rtnl_unlock();
> +
>  	kfree(buf);
>  }
>  
> +static void virtnet_set_rx_mode(struct net_device *dev)
> +{
> +	struct virtnet_info *vi = netdev_priv(dev);
> +
> +	if (vi->rx_mode_work_enabled)
> +		schedule_work(&vi->rx_mode_work);
> +}
> +

>  static int virtnet_vlan_rx_add_vid(struct net_device *dev,
>  				   __be16 proto, u16 vid)
>  {
> @@ -3181,6 +3222,8 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
>  
>  	/* Make sure no work handler is accessing the device */
>  	flush_work(&vi->config_work);
> +	disable_rx_mode_work(vi);
> +	flush_work(&vi->rx_mode_work);
>  
>  	netif_tx_lock_bh(vi->dev);
>  	netif_device_detach(vi->dev);

Hmm so queued rx mode work will just get skipped
and on restore we get a wrong rx mode.
Any way to make this more robust?

> @@ -3203,6 +3246,7 @@ static int virtnet_restore_up(struct virtio_device *vdev)
>  	virtio_device_ready(vdev);
>  
>  	enable_delayed_refill(vi);
> +	enable_rx_mode_work(vi);
>  
>  	if (netif_running(vi->dev)) {
>  		err = virtnet_open(vi->dev);
> @@ -4002,6 +4046,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	vdev->priv = vi;
>  
>  	INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> +	INIT_WORK(&vi->rx_mode_work, virtnet_rx_mode_work);
>  	spin_lock_init(&vi->refill_lock);
>  
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
> @@ -4110,6 +4155,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	if (vi->has_rss || vi->has_rss_hash_report)
>  		virtnet_init_default_rss(vi);
>  
> +	enable_rx_mode_work(vi);
> +
>  	/* serialize netdev register + virtio_device_ready() with ndo_open() */
>  	rtnl_lock();
>  
> @@ -4207,6 +4254,8 @@ static void virtnet_remove(struct virtio_device *vdev)
>  
>  	/* Make sure no work handler is accessing the device. */
>  	flush_work(&vi->config_work);
> +	disable_rx_mode_work(vi);
> +	flush_work(&vi->rx_mode_work);
>  
>  	unregister_netdev(vi->dev);
>  
> -- 
> 2.25.1