Message-ID: <1847406.lF1C9eqvK7@jason-thinkpad-t430s>
Date:	Mon, 03 Dec 2012 13:47:12 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	rusty@...tcorp.com.au, krkumar2@...ibm.com,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	bhutchings@...arflare.com, jwhan@...ewood.snu.ac.kr,
	shiyer@...hat.com
Subject: Re: [net-next rfc v7 2/3] virtio_net: multiqueue support

On Sunday, December 02, 2012 06:06:31 PM Michael S. Tsirkin wrote:
> 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 <krkumar2@...ibm.com>
> > Signed-off-by: Jason Wang <jasowang@...hat.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?

Oh, I miss the check of this part in v5. Have a thought about this, if we 
change the location of cvq, we may break the support of legacy guest with only 
single queue support. Consider we start a vm with 2 queue but boot a signle 
queue legacy guest, it may think vq 2 is cvq which indeed is rx1.
> 
> > +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.

Sure.
> 
> > +
> > +	/* 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.

Ok.
> 
> >  	/* 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?

Yes, will add a check of VIRTIO_NET_F_RFS before calling virtnet_set_queues().
> 
> >  	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 */
--
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