On Tue, Nov 27, 2012 at 06:15:59PM +0800, Jason Wang wrote:
> This addes multiqueue support to virtio_net driver. In multiple queue modes, 
> the
> driver expects the number of queue paris is equal to the number of vcpus. To
> eliminate the contention bettwen vcpus and virtqueues, per-cpu virtqueue pairs
> were implemented through:
> 
> - select the txq based on the smp processor id.
> - smp affinity hint were set to the vcpu that owns the queue pairs.
> 
> Signed-off-by: Krishna Kumar <krkum...@in.ibm.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
>  drivers/net/virtio_net.c        |  454 
> ++++++++++++++++++++++++++++++---------
>  include/uapi/linux/virtio_net.h |   16 ++
>  2 files changed, 371 insertions(+), 99 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7975133..bcaa6e5 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -84,17 +84,25 @@ struct virtnet_info {
>       struct virtio_device *vdev;
>       struct virtqueue *cvq;
>       struct net_device *dev;
> -     struct napi_struct napi;
> -     struct send_queue sq;
> -     struct receive_queue rq;
> +     struct send_queue *sq;
> +     struct receive_queue *rq;
>       unsigned int status;
>  
> +     /* Max # of queue pairs supported by the device */
> +     u16 max_queue_pairs;
> +
> +     /* # of queue pairs currently used by the driver */
> +     u16 curr_queue_pairs;
> +
>       /* I like... big packets and I cannot lie! */
>       bool big_packets;
>  
>       /* Host will merge rx buffers for big packets (shake it! shake it!) */
>       bool mergeable_rx_bufs;
>  
> +     /* Has control virtqueue */
> +     bool has_cvq;
> +
>       /* enable config space updates */
>       bool config_enable;
>  
> @@ -126,6 +134,34 @@ struct padded_vnet_hdr {
>       char padding[6];
>  };
>  
> +static const struct ethtool_ops virtnet_ethtool_ops;
> +
> +/*
> + * Converting between virtqueue no. and kernel tx/rx queue no.
> + * 0:rx0 1:tx0 2:cvq 3:rx1 4:tx1 ... 2N+1:rxN 2N+2:txN
> + */

Weird, this isn't what spec v5 says: it says
0:rx0 1:tx0 2: rx1 3: tx1 .... vcq
We can change the spec to match but keeping all rx/tx
together seems a bit prettier?

> +static int vq2txq(struct virtqueue *vq)
> +{
> +     int index = virtqueue_get_queue_index(vq);
> +     return index == 1 ? 0 : (index - 2) / 2;
> +}
> +
> +static int txq2vq(int txq)
> +{
> +     return txq ? 2 * txq + 2 : 1;
> +}
> +
> +static int vq2rxq(struct virtqueue *vq)
> +{
> +     int index = virtqueue_get_queue_index(vq);
> +     return index ? (index - 1) / 2 : 0;
> +}
> +
> +static int rxq2vq(int rxq)
> +{
> +     return rxq ? 2 * rxq + 1 : 0;
> +}
> +
>  static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
>  {
>       return (struct skb_vnet_hdr *)skb->cb;
> @@ -166,7 +202,7 @@ static void skb_xmit_done(struct virtqueue *vq)
>       virtqueue_disable_cb(vq);
>  
>       /* We were probably waiting for more output buffers. */
> -     netif_wake_queue(vi->dev);
> +     netif_wake_subqueue(vi->dev, vq2txq(vq));
>  }
>  
>  static void set_skb_frag(struct sk_buff *skb, struct page *page,
> @@ -503,7 +539,7 @@ static bool try_fill_recv(struct receive_queue *rq, gfp_t 
> gfp)
>  static void skb_recv_done(struct virtqueue *rvq)
>  {
>       struct virtnet_info *vi = rvq->vdev->priv;
> -     struct receive_queue *rq = &vi->rq;
> +     struct receive_queue *rq = &vi->rq[vq2rxq(rvq)];
>  
>       /* Schedule NAPI, Suppress further interrupts if successful. */
>       if (napi_schedule_prep(&rq->napi)) {
> @@ -650,7 +686,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff 
> *skb)
>  static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>  {
>       struct virtnet_info *vi = netdev_priv(dev);
> -     struct send_queue *sq = &vi->sq;
> +     int qnum = skb_get_queue_mapping(skb);
> +     struct send_queue *sq = &vi->sq[qnum];
>       int capacity;
>  
>       /* Free up any pending old buffers before queueing new ones. */
> @@ -664,13 +701,14 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, 
> struct net_device *dev)
>               if (likely(capacity == -ENOMEM)) {
>                       if (net_ratelimit())
>                               dev_warn(&dev->dev,
> -                                      "TX queue failure: out of memory\n");
> +                                      "TXQ (%d) failure: out of memory\n",
> +                                      qnum);
>               } else {
>                       dev->stats.tx_fifo_errors++;
>                       if (net_ratelimit())
>                               dev_warn(&dev->dev,
> -                                      "Unexpected TX queue failure: %d\n",
> -                                      capacity);
> +                                      "Unexpected TXQ (%d) failure: %d\n",
> +                                      qnum, capacity);
>               }
>               dev->stats.tx_dropped++;
>               kfree_skb(skb);
> @@ -685,12 +723,12 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, 
> struct net_device *dev)
>       /* Apparently nice girls don't return TX_BUSY; stop the queue
>        * before it gets out of hand.  Naturally, this wastes entries. */
>       if (capacity < 2+MAX_SKB_FRAGS) {
> -             netif_stop_queue(dev);
> +             netif_stop_subqueue(dev, qnum);
>               if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
>                       /* More just got used, free them then recheck. */
>                       capacity += free_old_xmit_skbs(sq);
>                       if (capacity >= 2+MAX_SKB_FRAGS) {
> -                             netif_start_queue(dev);
> +                             netif_start_subqueue(dev, qnum);
>                               virtqueue_disable_cb(sq->vq);
>                       }
>               }
> @@ -758,23 +796,13 @@ static struct rtnl_link_stats64 *virtnet_stats(struct 
> net_device *dev,
>  static void virtnet_netpoll(struct net_device *dev)
>  {
>       struct virtnet_info *vi = netdev_priv(dev);
> +     int i;
>  
> -     napi_schedule(&vi->rq.napi);
> +     for (i = 0; i < vi->curr_queue_pairs; i++)
> +             napi_schedule(&vi->rq[i].napi);
>  }
>  #endif
>  
> -static int virtnet_open(struct net_device *dev)
> -{
> -     struct virtnet_info *vi = netdev_priv(dev);
> -
> -     /* Make sure we have some buffers: if oom use wq. */
> -     if (!try_fill_recv(&vi->rq, GFP_KERNEL))
> -             schedule_delayed_work(&vi->rq.refill, 0);
> -
> -     virtnet_napi_enable(&vi->rq);
> -     return 0;
> -}
> -
>  /*
>   * Send command via the control virtqueue and check status.  Commands
>   * supported by the hypervisor, as indicated by feature bits, should
> @@ -830,13 +858,53 @@ static void virtnet_ack_link_announce(struct 
> virtnet_info *vi)
>       rtnl_unlock();
>  }
>  
> +static int virtnet_set_queues(struct virtnet_info *vi)
> +{
> +     struct scatterlist sg;
> +     struct virtio_net_ctrl_rfs s;
> +     struct net_device *dev = vi->dev;
> +
> +     s.virtqueue_pairs = vi->curr_queue_pairs;
> +     sg_init_one(&sg, &s, sizeof(s));
> +
> +     if (!vi->has_cvq)
> +             return -EINVAL;
> +
> +     if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RFS,
> +                               VIRTIO_NET_CTRL_RFS_VQ_PAIRS_SET, &sg, 1, 0)){
> +             dev_warn(&dev->dev, "Fail to set the number of queue pairs to"
> +                      " %d\n", vi->curr_queue_pairs);
> +             return -EINVAL;
> +     }
> +
> +     return 0;
> +}
> +
> +static int virtnet_open(struct net_device *dev)
> +{
> +     struct virtnet_info *vi = netdev_priv(dev);
> +     int i;
> +
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             /* Make sure we have some buffers: if oom use wq. */
> +             if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
> +                     schedule_delayed_work(&vi->rq[i].refill, 0);
> +             virtnet_napi_enable(&vi->rq[i]);
> +     }
> +
> +     return 0;
> +}
> +
>  static int virtnet_close(struct net_device *dev)
>  {
>       struct virtnet_info *vi = netdev_priv(dev);
> +     int i;
>  
>       /* Make sure refill_work doesn't re-enable napi! */
> -     cancel_delayed_work_sync(&vi->rq.refill);
> -     napi_disable(&vi->rq.napi);
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             cancel_delayed_work_sync(&vi->rq[i].refill);
> +             napi_disable(&vi->rq[i].napi);
> +     }
>  
>       return 0;
>  }
> @@ -948,8 +1016,8 @@ static void virtnet_get_ringparam(struct net_device *dev,
>  {
>       struct virtnet_info *vi = netdev_priv(dev);
>  
> -     ring->rx_max_pending = virtqueue_get_vring_size(vi->rq.vq);
> -     ring->tx_max_pending = virtqueue_get_vring_size(vi->sq.vq);
> +     ring->rx_max_pending = virtqueue_get_vring_size(vi->rq[0].vq);
> +     ring->tx_max_pending = virtqueue_get_vring_size(vi->sq[0].vq);
>       ring->rx_pending = ring->rx_max_pending;
>       ring->tx_pending = ring->tx_max_pending;
>  }
> @@ -967,12 +1035,6 @@ static void virtnet_get_drvinfo(struct net_device *dev,
>  
>  }
>  
> -static const struct ethtool_ops virtnet_ethtool_ops = {
> -     .get_drvinfo = virtnet_get_drvinfo,
> -     .get_link = ethtool_op_get_link,
> -     .get_ringparam = virtnet_get_ringparam,
> -};
> -
>  #define MIN_MTU 68
>  #define MAX_MTU 65535
>  
> @@ -984,6 +1046,20 @@ static int virtnet_change_mtu(struct net_device *dev, 
> int new_mtu)
>       return 0;
>  }
>  
> +/* To avoid contending a lock hold by a vcpu who would exit to host, select 
> the
> + * txq based on the processor id.
> + */
> +static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb)
> +{
> +     int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) :
> +               smp_processor_id();
> +
> +     while (unlikely(txq >= dev->real_num_tx_queues))
> +             txq -= dev->real_num_tx_queues;
> +
> +     return txq;
> +}
> +
>  static const struct net_device_ops virtnet_netdev = {
>       .ndo_open            = virtnet_open,
>       .ndo_stop            = virtnet_close,
> @@ -995,6 +1071,7 @@ static const struct net_device_ops virtnet_netdev = {
>       .ndo_get_stats64     = virtnet_stats,
>       .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
>       .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
> +     .ndo_select_queue     = virtnet_select_queue,
>  #ifdef CONFIG_NET_POLL_CONTROLLER
>       .ndo_poll_controller = virtnet_netpoll,
>  #endif
> @@ -1030,10 +1107,10 @@ static void virtnet_config_changed_work(struct 
> work_struct *work)
>  
>       if (vi->status & VIRTIO_NET_S_LINK_UP) {
>               netif_carrier_on(vi->dev);
> -             netif_wake_queue(vi->dev);
> +             netif_tx_wake_all_queues(vi->dev);
>       } else {
>               netif_carrier_off(vi->dev);
> -             netif_stop_queue(vi->dev);
> +             netif_tx_stop_all_queues(vi->dev);
>       }
>  done:
>       mutex_unlock(&vi->config_lock);
> @@ -1046,41 +1123,212 @@ static void virtnet_config_changed(struct 
> virtio_device *vdev)
>       schedule_work(&vi->config_work);
>  }
>  
> -static int init_vqs(struct virtnet_info *vi)
> +static void free_receive_bufs(struct virtnet_info *vi)
> +{
> +     int i;
> +
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             while (vi->rq[i].pages)
> +                     __free_pages(get_a_page(&vi->rq[i], GFP_KERNEL), 0);
> +     }
> +}
> +
> +/* Free memory allocated for send and receive queues */
> +static void virtnet_free_queues(struct virtnet_info *vi)
>  {
> -     struct virtqueue *vqs[3];
> -     vq_callback_t *callbacks[] = { skb_recv_done, skb_xmit_done, NULL};
> -     const char *names[] = { "input", "output", "control" };
> -     int nvqs, err;
> +     kfree(vi->rq);
> +     vi->rq = NULL;
> +     kfree(vi->sq);
> +     vi->sq = NULL;
> +}
>  
> -     /* We expect two virtqueues, receive then send,
> -      * and optionally control. */
> -     nvqs = virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ? 3 : 2;
> +static void free_unused_bufs(struct virtnet_info *vi)
> +{
> +     void *buf;
> +     int i;
>  
> -     err = vi->vdev->config->find_vqs(vi->vdev, nvqs, vqs, callbacks, names);
> -     if (err)
> -             return err;
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             struct virtqueue *vq = vi->sq[i].vq;
> +             while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> +                     dev_kfree_skb(buf);
> +     }
>  
> -     vi->rq.vq = vqs[0];
> -     vi->sq.vq = vqs[1];
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             struct virtqueue *vq = vi->rq[i].vq;
>  
> -     if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
> -             vi->cvq = vqs[2];
> +             while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
> +                     if (vi->mergeable_rx_bufs || vi->big_packets)
> +                             give_pages(&vi->rq[i], buf);
> +                     else
> +                             dev_kfree_skb(buf);
> +                     --vi->rq[i].num;
> +             }
> +             BUG_ON(vi->rq[i].num != 0);
> +     }
> +}
>  
> +static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
> +{
> +     int i;
> +
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             int cpu = set ? i : -1;
> +             virtqueue_set_affinity(vi->rq[i].vq, cpu);
> +             virtqueue_set_affinity(vi->sq[i].vq, cpu);
> +     }
> +}
> +
> +static void virtnet_del_vqs(struct virtnet_info *vi)
> +{
> +     struct virtio_device *vdev = vi->vdev;
> +
> +     virtnet_set_affinity(vi, false);
> +
> +     vdev->config->del_vqs(vdev);
> +
> +     virtnet_free_queues(vi);
> +}
> +
> +static int virtnet_find_vqs(struct virtnet_info *vi)
> +{
> +     vq_callback_t **callbacks;
> +     struct virtqueue **vqs;
> +     int ret = -ENOMEM;
> +     int i, total_vqs;
> +     char **names;
> +
> +     /*
> +      * We expect 1 RX virtqueue followed by 1 TX virtqueue, followd by
> +      * possible control virtqueue, followed by RX/TX N-1 queue pairs used
> +      * in multiqueue mode.
> +      */
> +     total_vqs = vi->max_queue_pairs * 2 +
> +                 virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ);
> +
> +     /* Allocate space for find_vqs parameters */
> +     vqs = kzalloc(total_vqs * sizeof(*vqs), GFP_KERNEL);
> +     callbacks = kzalloc(total_vqs * sizeof(*callbacks), GFP_KERNEL);
> +     if (!vqs || !callbacks)
> +             goto err_mem;
> +     names = kzalloc(total_vqs * sizeof(*names), GFP_KERNEL);
> +     if (!names)
> +             goto err_mem;
> +
> +     /* Parameters for control virtqueue, if any */
> +     if (vi->has_cvq) {
> +             callbacks[2] = NULL;
> +             names[2] = kasprintf(GFP_KERNEL, "control");
> +     }
> +
> +     /* Allocate/initialize parameters for send/receive virtqueues */
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             callbacks[rxq2vq(i)] = skb_recv_done;
> +             callbacks[txq2vq(i)] = skb_xmit_done;
> +             names[rxq2vq(i)] = kasprintf(GFP_KERNEL, "input.%d", i);
> +             names[txq2vq(i)] = kasprintf(GFP_KERNEL, "output.%d", i);
> +     }
> +
> +     ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
> +                                      (const char **)names);
> +     if (ret)
> +             goto err_names;
> +
> +     if (vi->has_cvq) {
> +             vi->cvq = vqs[2];
>               if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
>                       vi->dev->features |= NETIF_F_HW_VLAN_FILTER;
>       }
> +
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             vi->rq[i].vq = vqs[rxq2vq(i)];
> +             vi->sq[i].vq = vqs[txq2vq(i)];
> +     }
> +
> +     kfree(callbacks);
> +     kfree(vqs);
> +
> +     return 0;
> +
> +err_names:
> +     for (i = 0; i < total_vqs * 2; i ++)
> +             kfree(names[i]);
> +     kfree(names);
> +
> +err_mem:
> +     kfree(callbacks);
> +     kfree(vqs);
> +
> +     return ret;
> +}
> +
> +static int virtnet_alloc_queues(struct virtnet_info *vi)
> +{
> +     int i;
> +
> +     vi->sq = kzalloc(sizeof(vi->sq[0]) * vi->max_queue_pairs, GFP_KERNEL);
> +     vi->rq = kzalloc(sizeof(vi->rq[0]) * vi->max_queue_pairs, GFP_KERNEL);
> +     if (!vi->rq || !vi->sq)
> +             goto err;
> +
> +     /* setup initial receive and send queue parameters */
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             vi->rq[i].pages = NULL;
> +             INIT_DELAYED_WORK(&vi->rq[i].refill, refill_work);
> +             netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll,
> +                            napi_weight);
> +
> +             sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
> +             sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
> +     }
> +
> +
>       return 0;
> +
> +err:
> +     virtnet_free_queues(vi);
> +     return -ENOMEM;
> +}
> +
> +static int init_vqs(struct virtnet_info *vi)
> +{
> +     int ret;
> +
> +     /* Allocate send & receive queues */
> +     ret = virtnet_alloc_queues(vi);
> +     if (ret)
> +             goto err;
> +
> +     ret = virtnet_find_vqs(vi);
> +     if (ret)
> +             goto err_free;
> +
> +     virtnet_set_affinity(vi, true);
> +     return 0;
> +
> +err_free:
> +     virtnet_free_queues(vi);
> +err:
> +     return ret;
>  }
>  
>  static int virtnet_probe(struct virtio_device *vdev)
>  {
> -     int err;
> +     int i, err;
>       struct net_device *dev;
>       struct virtnet_info *vi;
> +     u16 curr_queue_pairs;

Probably a good idea to rename this max_queue_pairs.

> +
> +     /* Find if host supports multiqueue virtio_net device */
> +     err = virtio_config_val(vdev, VIRTIO_NET_F_RFS,
> +                             offsetof(struct virtio_net_config,
> +                             max_virtqueue_pairs), &curr_queue_pairs);
> +
> +     /* We need at least 2 queue's */
> +     if (err)
> +             curr_queue_pairs = 1;

Let's also validate against VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MIN
and VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MAX.

>  
>       /* Allocate ourselves a network device with room for our info */
> -     dev = alloc_etherdev(sizeof(struct virtnet_info));
> +     dev = alloc_etherdev_mq(sizeof(struct virtnet_info), curr_queue_pairs);
>       if (!dev)
>               return -ENOMEM;
>  
> @@ -1126,22 +1374,17 @@ static int virtnet_probe(struct virtio_device *vdev)
>  
>       /* Set up our device-specific information */
>       vi = netdev_priv(dev);
> -     netif_napi_add(dev, &vi->rq.napi, virtnet_poll, napi_weight);
>       vi->dev = dev;
>       vi->vdev = vdev;
>       vdev->priv = vi;
> -     vi->rq.pages = NULL;
>       vi->stats = alloc_percpu(struct virtnet_stats);
>       err = -ENOMEM;
>       if (vi->stats == NULL)
>               goto free;
>  
> -     INIT_DELAYED_WORK(&vi->rq.refill, refill_work);
>       mutex_init(&vi->config_lock);
>       vi->config_enable = true;
>       INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> -     sg_init_table(vi->rq.sg, ARRAY_SIZE(vi->rq.sg));
> -     sg_init_table(vi->sq.sg, ARRAY_SIZE(vi->sq.sg));
>  
>       /* If we can receive ANY GSO packets, we must allocate large ones. */
>       if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> @@ -1152,10 +1395,21 @@ static int virtnet_probe(struct virtio_device *vdev)
>       if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
>               vi->mergeable_rx_bufs = true;
>  
> +     if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
> +             vi->has_cvq = true;
> +
> +     /* Use single tx/rx queue pair as default */
> +     vi->curr_queue_pairs = 1;
> +     vi->max_queue_pairs = curr_queue_pairs;
> +
> +     /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
>       err = init_vqs(vi);
>       if (err)
>               goto free_stats;
>  
> +     netif_set_real_num_tx_queues(dev, 1);
> +     netif_set_real_num_rx_queues(dev, 1);
> +
>       err = register_netdev(dev);
>       if (err) {
>               pr_debug("virtio_net: registering device failed\n");
> @@ -1163,12 +1417,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>       }
>  
>       /* Last of all, set up some receive buffers. */
> -     try_fill_recv(&vi->rq, GFP_KERNEL);
> -
> -     /* If we didn't even get one input buffer, we're useless. */
> -     if (vi->rq.num == 0) {
> -             err = -ENOMEM;
> -             goto unregister;
> +     for (i = 0; i < vi->max_queue_pairs; i++) {
> +             try_fill_recv(&vi->rq[i], GFP_KERNEL);
> +
> +             /* If we didn't even get one input buffer, we're useless. */
> +             if (vi->rq[i].num == 0) {
> +                     free_unused_bufs(vi);
> +                     err = -ENOMEM;
> +                     goto free_recv_bufs;
> +             }
>       }
>  
>       /* Assume link up if device can't report link status,
> @@ -1181,13 +1438,20 @@ static int virtnet_probe(struct virtio_device *vdev)
>               netif_carrier_on(dev);
>       }
>  
> -     pr_debug("virtnet: registered device %s\n", dev->name);
> +     pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
> +              dev->name, curr_queue_pairs);
> +
>       return 0;
>  
> -unregister:
> +free_recv_bufs:
> +     free_receive_bufs(vi);
>       unregister_netdev(dev);
> +
>  free_vqs:
> -     vdev->config->del_vqs(vdev);
> +     for (i = 0; i <curr_queue_pairs; i++)
> +             cancel_delayed_work_sync(&vi->rq[i].refill);
> +     virtnet_del_vqs(vi);
> +
>  free_stats:
>       free_percpu(vi->stats);
>  free:
> @@ -1195,28 +1459,6 @@ free:
>       return err;
>  }
>  
> -static void free_unused_bufs(struct virtnet_info *vi)
> -{
> -     void *buf;
> -     while (1) {
> -             buf = virtqueue_detach_unused_buf(vi->sq.vq);
> -             if (!buf)
> -                     break;
> -             dev_kfree_skb(buf);
> -     }
> -     while (1) {
> -             buf = virtqueue_detach_unused_buf(vi->rq.vq);
> -             if (!buf)
> -                     break;
> -             if (vi->mergeable_rx_bufs || vi->big_packets)
> -                     give_pages(&vi->rq, buf);
> -             else
> -                     dev_kfree_skb(buf);
> -             --vi->rq.num;
> -     }
> -     BUG_ON(vi->rq.num != 0);
> -}
> -
>  static void remove_vq_common(struct virtnet_info *vi)
>  {
>       vi->vdev->config->reset(vi->vdev);
> @@ -1224,10 +1466,9 @@ static void remove_vq_common(struct virtnet_info *vi)
>       /* Free unused buffers in both send and recv, if any. */
>       free_unused_bufs(vi);
>  
> -     vi->vdev->config->del_vqs(vi->vdev);
> +     free_receive_bufs(vi);
>  
> -     while (vi->rq.pages)
> -             __free_pages(get_a_page(&vi->rq, GFP_KERNEL), 0);
> +     virtnet_del_vqs(vi);
>  }
>  
>  static void __devexit virtnet_remove(struct virtio_device *vdev)
> @@ -1253,6 +1494,7 @@ static void __devexit virtnet_remove(struct 
> virtio_device *vdev)
>  static int virtnet_freeze(struct virtio_device *vdev)
>  {
>       struct virtnet_info *vi = vdev->priv;
> +     int i;
>  
>       /* Prevent config work handler from accessing the device */
>       mutex_lock(&vi->config_lock);
> @@ -1260,10 +1502,14 @@ static int virtnet_freeze(struct virtio_device *vdev)
>       mutex_unlock(&vi->config_lock);
>  
>       netif_device_detach(vi->dev);
> -     cancel_delayed_work_sync(&vi->rq.refill);
> +     for (i = 0; i < vi->max_queue_pairs; i++)
> +             cancel_delayed_work_sync(&vi->rq[i].refill);
>  
>       if (netif_running(vi->dev))
> -             napi_disable(&vi->rq.napi);
> +             for (i = 0; i < vi->max_queue_pairs; i++) {
> +                     napi_disable(&vi->rq[i].napi);
> +                     netif_napi_del(&vi->rq[i].napi);
> +             }
>  
>       remove_vq_common(vi);
>  
> @@ -1275,24 +1521,28 @@ static int virtnet_freeze(struct virtio_device *vdev)
>  static int virtnet_restore(struct virtio_device *vdev)
>  {
>       struct virtnet_info *vi = vdev->priv;
> -     int err;
> +     int err, i;
>  
>       err = init_vqs(vi);
>       if (err)
>               return err;
>  
>       if (netif_running(vi->dev))
> -             virtnet_napi_enable(&vi->rq);
> +             for (i = 0; i < vi->max_queue_pairs; i++)
> +                     virtnet_napi_enable(&vi->rq[i]);
>  
>       netif_device_attach(vi->dev);
>  
> -     if (!try_fill_recv(&vi->rq, GFP_KERNEL))
> -             schedule_delayed_work(&vi->rq.refill, 0);
> +     for (i = 0; i < vi->max_queue_pairs; i++)
> +             if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
> +                     schedule_delayed_work(&vi->rq[i].refill, 0);
>  
>       mutex_lock(&vi->config_lock);
>       vi->config_enable = true;
>       mutex_unlock(&vi->config_lock);
>  
> +     BUG_ON(virtnet_set_queues(vi));
> +

Won't this always fail when control vq is off?

>       return 0;
>  }
>  #endif
> @@ -1310,7 +1560,7 @@ static unsigned int features[] = {
>       VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
>       VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
>       VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
> -     VIRTIO_NET_F_GUEST_ANNOUNCE,
> +     VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_RFS,
>  };
>  
>  static struct virtio_driver virtio_net_driver = {
> @@ -1328,6 +1578,12 @@ static struct virtio_driver virtio_net_driver = {
>  #endif
>  };
>  
> +static const struct ethtool_ops virtnet_ethtool_ops = {
> +     .get_drvinfo = virtnet_get_drvinfo,
> +     .get_link = ethtool_op_get_link,
> +     .get_ringparam = virtnet_get_ringparam,
> +};
> +
>  static int __init init(void)
>  {
>       return register_virtio_driver(&virtio_net_driver);
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index 2470f54..6056cec 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -51,6 +51,7 @@
>  #define VIRTIO_NET_F_CTRL_RX_EXTRA 20        /* Extra RX mode control 
> support */
>  #define VIRTIO_NET_F_GUEST_ANNOUNCE 21       /* Guest can announce device on 
> the
>                                        * network */
> +#define VIRTIO_NET_F_RFS     22      /* Device supports multiple TXQ/RXQ */
>  
>  #define VIRTIO_NET_S_LINK_UP 1       /* Link is up */
>  #define VIRTIO_NET_S_ANNOUNCE        2       /* Announcement is needed */
> @@ -60,6 +61,8 @@ struct virtio_net_config {
>       __u8 mac[6];
>       /* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
>       __u16 status;
> +     /* Total number of RX/TX queues */
> +     __u16 max_virtqueue_pairs;
>  } __attribute__((packed));
>  
>  /* This is the first element of the scatter-gather list.  If you don't
> @@ -166,4 +169,17 @@ struct virtio_net_ctrl_mac {
>  #define VIRTIO_NET_CTRL_ANNOUNCE       3
>   #define VIRTIO_NET_CTRL_ANNOUNCE_ACK         0
>  
> +/*
> + * Control multiqueue
> + *
> + */
> +struct virtio_net_ctrl_rfs {
> +     u16 virtqueue_pairs;
> +};
> +
> +#define VIRTIO_NET_CTRL_RFS   4
> + #define VIRTIO_NET_CTRL_RFS_VQ_PAIRS_SET        0
> + #define VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MIN        1
> + #define VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MAX        0x8000
> +
>  #endif /* _LINUX_VIRTIO_NET_H */
> -- 
> 1.7.1
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