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Date:   Tue, 16 Aug 2022 02:31:22 +0000
From:   Bobby Eshleman <bobbyeshleman@gmail.com>
To:     Bobby Eshleman <bobby.eshleman@gmail.com>
Cc:     virtio-dev@lists.oasis-open.org,
        Bobby Eshleman <bobby.eshleman@bytedance.com>,
        Cong Wang <cong.wang@bytedance.com>,
        Jiang Wang <jiang.wang@bytedance.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/6] vsock: add netdev to vhost/virtio vsock
Message-ID: <YvsBei6p30vw7b9I@bullseye>
References: <cover.1660362668.git.bobby.eshleman@bytedance.com>
 <5a93c5aad99d79f028d349cb7e3c128c65d5d7e2.1660362668.git.bobby.eshleman@bytedance.com>
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CC'ing virtio-dev@lists.oasis-open.org

On Mon, Aug 15, 2022 at 10:56:06AM -0700, Bobby Eshleman wrote:
> In order to support usage of qdisc on vsock traffic, this commit
> introduces a struct net_device to vhost and virtio vsock.
> 
> Two new devices are created, vhost-vsock for vhost and virtio-vsock
> for virtio. The devices are attached to the respective transports.
> 
> To bypass the usage of the device, the user may "down" the associated
> network interface using common tools. For example, "ip link set dev
> virtio-vsock down" lets vsock bypass the net_device and qdisc entirely,
> simply using the FIFO logic of the prior implementation.
> 
> For both hosts and guests, there is one device for all G2H vsock sockets
> and one device for all H2G vsock sockets. This makes sense for guests
> because the driver only supports a single vsock channel (one pair of
> TX/RX virtqueues), so one device and qdisc fits. For hosts, this may not
> seem ideal for some workloads. However, it is possible to use a
> multi-queue qdisc, where a given queue is responsible for a range of
> sockets. This seems to be a better solution than having one device per
> socket, which may yield a very large number of devices and qdiscs, all
> of which are dynamically being created and destroyed. Because of this
> dynamism, it would also require a complex policy management daemon, as
> devices would constantly be spun up and down as sockets were created and
> destroyed. To avoid this, one device and qdisc also applies to all H2G
> sockets.
> 
> Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
> ---
>  drivers/vhost/vsock.c                   |  19 +++-
>  include/linux/virtio_vsock.h            |  10 +++
>  net/vmw_vsock/virtio_transport.c        |  19 +++-
>  net/vmw_vsock/virtio_transport_common.c | 112 +++++++++++++++++++++++-
>  4 files changed, 152 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index f8601d93d94d..b20ddec2664b 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -927,13 +927,30 @@ static int __init vhost_vsock_init(void)
>  				  VSOCK_TRANSPORT_F_H2G);
>  	if (ret < 0)
>  		return ret;
> -	return misc_register(&vhost_vsock_misc);
> +
> +	ret = virtio_transport_init(&vhost_transport, "vhost-vsock");
> +	if (ret < 0)
> +		goto out_unregister;
> +
> +	ret = misc_register(&vhost_vsock_misc);
> +	if (ret < 0)
> +		goto out_transport_exit;
> +	return ret;
> +
> +out_transport_exit:
> +	virtio_transport_exit(&vhost_transport);
> +
> +out_unregister:
> +	vsock_core_unregister(&vhost_transport.transport);
> +	return ret;
> +
>  };
>  
>  static void __exit vhost_vsock_exit(void)
>  {
>  	misc_deregister(&vhost_vsock_misc);
>  	vsock_core_unregister(&vhost_transport.transport);
> +	virtio_transport_exit(&vhost_transport);
>  };
>  
>  module_init(vhost_vsock_init);
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index 9a37eddbb87a..5d7e7fbd75f8 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -91,10 +91,20 @@ struct virtio_transport {
>  	/* This must be the first field */
>  	struct vsock_transport transport;
>  
> +	/* Used almost exclusively for qdisc */
> +	struct net_device *dev;
> +
>  	/* Takes ownership of the packet */
>  	int (*send_pkt)(struct sk_buff *skb);
>  };
>  
> +int
> +virtio_transport_init(struct virtio_transport *t,
> +		      const char *name);
> +
> +void
> +virtio_transport_exit(struct virtio_transport *t);
> +
>  ssize_t
>  virtio_transport_stream_dequeue(struct vsock_sock *vsk,
>  				struct msghdr *msg,
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index 3bb293fd8607..c6212eb38d3c 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -131,7 +131,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>  		 * the vq
>  		 */
>  		if (ret < 0) {
> -			skb_queue_head(&vsock->send_pkt_queue, skb);
> +			spin_lock_bh(&vsock->send_pkt_queue.lock);
> +			__skb_queue_head(&vsock->send_pkt_queue, skb);
> +			spin_unlock_bh(&vsock->send_pkt_queue.lock);
>  			break;
>  		}
>  
> @@ -676,7 +678,9 @@ static void virtio_vsock_vqs_del(struct virtio_vsock *vsock)
>  		kfree_skb(skb);
>  	mutex_unlock(&vsock->tx_lock);
>  
> -	skb_queue_purge(&vsock->send_pkt_queue);
> +	spin_lock_bh(&vsock->send_pkt_queue.lock);
> +	__skb_queue_purge(&vsock->send_pkt_queue);
> +	spin_unlock_bh(&vsock->send_pkt_queue.lock);
>  
>  	/* Delete virtqueues and flush outstanding callbacks if any */
>  	vdev->config->del_vqs(vdev);
> @@ -760,6 +764,8 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>  	flush_work(&vsock->event_work);
>  	flush_work(&vsock->send_pkt_work);
>  
> +	virtio_transport_exit(&virtio_transport);
> +
>  	mutex_unlock(&the_virtio_vsock_mutex);
>  
>  	kfree(vsock);
> @@ -844,12 +850,18 @@ static int __init virtio_vsock_init(void)
>  	if (ret)
>  		goto out_wq;
>  
> -	ret = register_virtio_driver(&virtio_vsock_driver);
> +	ret = virtio_transport_init(&virtio_transport, "virtio-vsock");
>  	if (ret)
>  		goto out_vci;
>  
> +	ret = register_virtio_driver(&virtio_vsock_driver);
> +	if (ret)
> +		goto out_transport;
> +
>  	return 0;
>  
> +out_transport:
> +	virtio_transport_exit(&virtio_transport);
>  out_vci:
>  	vsock_core_unregister(&virtio_transport.transport);
>  out_wq:
> @@ -861,6 +873,7 @@ static void __exit virtio_vsock_exit(void)
>  {
>  	unregister_virtio_driver(&virtio_vsock_driver);
>  	vsock_core_unregister(&virtio_transport.transport);
> +	virtio_transport_exit(&virtio_transport);
>  	destroy_workqueue(virtio_vsock_workqueue);
>  }
>  
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index d5780599fe93..bdf16fff054f 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -16,6 +16,7 @@
>  
>  #include <net/sock.h>
>  #include <net/af_vsock.h>
> +#include <net/pkt_sched.h>
>  
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/vsock_virtio_transport_common.h>
> @@ -23,6 +24,93 @@
>  /* How long to wait for graceful shutdown of a connection */
>  #define VSOCK_CLOSE_TIMEOUT (8 * HZ)
>  
> +struct virtio_transport_priv {
> +	struct virtio_transport *trans;
> +};
> +
> +static netdev_tx_t virtio_transport_start_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> +	struct virtio_transport *t =
> +		((struct virtio_transport_priv *)netdev_priv(dev))->trans;
> +	int ret;
> +
> +	ret = t->send_pkt(skb);
> +	if (unlikely(ret == -ENODEV))
> +		return NETDEV_TX_BUSY;
> +
> +	return NETDEV_TX_OK;
> +}
> +
> +const struct net_device_ops virtio_transport_netdev_ops = {
> +	.ndo_start_xmit = virtio_transport_start_xmit,
> +};
> +
> +static void virtio_transport_setup(struct net_device *dev)
> +{
> +	dev->netdev_ops = &virtio_transport_netdev_ops;
> +	dev->needs_free_netdev = true;
> +	dev->flags = IFF_NOARP;
> +	dev->mtu = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
> +	dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
> +}
> +
> +static int ifup(struct net_device *dev)
> +{
> +	int ret;
> +
> +	rtnl_lock();
> +	ret = dev_open(dev, NULL) ? -ENOMEM : 0;
> +	rtnl_unlock();
> +
> +	return ret;
> +}
> +
> +/* virtio_transport_init - initialize a virtio vsock transport layer
> + *
> + * @t: ptr to the virtio transport struct to initialize
> + * @name: the name of the net_device to be created.
> + *
> + * Return 0 on success, otherwise negative errno.
> + */
> +int virtio_transport_init(struct virtio_transport *t, const char *name)
> +{
> +	struct virtio_transport_priv *priv;
> +	int ret;
> +
> +	t->dev = alloc_netdev(sizeof(*priv), name, NET_NAME_UNKNOWN, virtio_transport_setup);
> +	if (!t->dev)
> +		return -ENOMEM;
> +
> +	priv = netdev_priv(t->dev);
> +	priv->trans = t;
> +
> +	ret = register_netdev(t->dev);
> +	if (ret < 0)
> +		goto out_free_netdev;
> +
> +	ret = ifup(t->dev);
> +	if (ret < 0)
> +		goto out_unregister_netdev;
> +
> +	return 0;
> +
> +out_unregister_netdev:
> +	unregister_netdev(t->dev);
> +
> +out_free_netdev:
> +	free_netdev(t->dev);
> +
> +	return ret;
> +}
> +
> +void virtio_transport_exit(struct virtio_transport *t)
> +{
> +	if (t->dev) {
> +		unregister_netdev(t->dev);
> +		free_netdev(t->dev);
> +	}
> +}
> +
>  static const struct virtio_transport *
>  virtio_transport_get_ops(struct vsock_sock *vsk)
>  {
> @@ -147,6 +235,24 @@ static u16 virtio_transport_get_type(struct sock *sk)
>  		return VIRTIO_VSOCK_TYPE_SEQPACKET;
>  }
>  
> +/* Return pkt->len on success, otherwise negative errno */
> +static int virtio_transport_send_pkt(const struct virtio_transport *t, struct sk_buff *skb)
> +{
> +	int ret;
> +	int len = skb->len;
> +
> +	if (unlikely(!t->dev || !(t->dev->flags & IFF_UP)))
> +		return t->send_pkt(skb);
> +
> +	skb->dev = t->dev;
> +	ret = dev_queue_xmit(skb);
> +
> +	if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN))
> +		return len;
> +
> +	return -ENOMEM;
> +}
> +
>  /* This function can only be used on connecting/connected sockets,
>   * since a socket assigned to a transport is required.
>   *
> @@ -202,9 +308,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
>  
>  	virtio_transport_inc_tx_pkt(vvs, skb);
>  
> -	err = t_ops->send_pkt(skb);
> -
> -	return err < 0 ? -ENOMEM : err;
> +	return virtio_transport_send_pkt(t_ops, skb);
>  }
>  
>  static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
> @@ -834,7 +938,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
>  		return -ENOTCONN;
>  	}
>  
> -	return t->send_pkt(reply);
> +	return virtio_transport_send_pkt(t, reply);
>  }
>  
>  /* This function should be called with sk_lock held and SOCK_DONE set */
> -- 
> 2.35.1
>