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Commit 1565c7c1 authored by Krishna Kumar's avatar Krishna Kumar Committed by David S. Miller
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macvtap: Implement multiqueue for macvtap driver



Implement multiqueue facility for macvtap driver. The idea is that
a macvtap device can be opened multiple times and the fd's can be
used to register eg, as backend for vhost.

Signed-off-by: default avatarKrishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bfb564e7
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+82 −17
Original line number Diff line number Diff line
@@ -84,26 +84,45 @@ static const struct proto_ops macvtap_socket_ops;
static DEFINE_SPINLOCK(macvtap_lock);

/*
 * Choose the next free queue, for now there is only one
 * get_slot: return a [unused/occupied] slot in vlan->taps[]:
 *	- if 'q' is NULL, return the first empty slot;
 *	- otherwise, return the slot this pointer occupies.
 */
static int get_slot(struct macvlan_dev *vlan, struct macvtap_queue *q)
{
	int i;

	for (i = 0; i < MAX_MACVTAP_QUEUES; i++) {
		if (rcu_dereference(vlan->taps[i]) == q)
			return i;
	}

	/* Should never happen */
	BUG_ON(1);
}

static int macvtap_set_queue(struct net_device *dev, struct file *file,
				struct macvtap_queue *q)
{
	struct macvlan_dev *vlan = netdev_priv(dev);
	int index;
	int err = -EBUSY;

	spin_lock(&macvtap_lock);
	if (rcu_dereference(vlan->tap))
	if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
		goto out;

	err = 0;
	index = get_slot(vlan, NULL);
	rcu_assign_pointer(q->vlan, vlan);
	rcu_assign_pointer(vlan->tap, q);
	rcu_assign_pointer(vlan->taps[index], q);
	sock_hold(&q->sk);

	q->file = file;
	file->private_data = q;

	vlan->numvtaps++;

out:
	spin_unlock(&macvtap_lock);
	return err;
@@ -124,9 +143,12 @@ static void macvtap_put_queue(struct macvtap_queue *q)
	spin_lock(&macvtap_lock);
	vlan = rcu_dereference(q->vlan);
	if (vlan) {
		rcu_assign_pointer(vlan->tap, NULL);
		int index = get_slot(vlan, q);

		rcu_assign_pointer(vlan->taps[index], NULL);
		rcu_assign_pointer(q->vlan, NULL);
		sock_put(&q->sk);
		--vlan->numvtaps;
	}

	spin_unlock(&macvtap_lock);
@@ -136,39 +158,82 @@ static void macvtap_put_queue(struct macvtap_queue *q)
}

/*
 * Since we only support one queue, just dereference the pointer.
 * Select a queue based on the rxq of the device on which this packet
 * arrived. If the incoming device is not mq, calculate a flow hash
 * to select a queue. If all fails, find the first available queue.
 * Cache vlan->numvtaps since it can become zero during the execution
 * of this function.
 */
static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
					       struct sk_buff *skb)
{
	struct macvlan_dev *vlan = netdev_priv(dev);
	struct macvtap_queue *tap = NULL;
	int numvtaps = vlan->numvtaps;
	__u32 rxq;

	return rcu_dereference(vlan->tap);
	if (!numvtaps)
		goto out;

	if (likely(skb_rx_queue_recorded(skb))) {
		rxq = skb_get_rx_queue(skb);

		while (unlikely(rxq >= numvtaps))
			rxq -= numvtaps;

		tap = rcu_dereference(vlan->taps[rxq]);
		if (tap)
			goto out;
	}

	/* Check if we can use flow to select a queue */
	rxq = skb_get_rxhash(skb);
	if (rxq) {
		tap = rcu_dereference(vlan->taps[rxq % numvtaps]);
		if (tap)
			goto out;
	}

	/* Everything failed - find first available queue */
	for (rxq = 0; rxq < MAX_MACVTAP_QUEUES; rxq++) {
		tap = rcu_dereference(vlan->taps[rxq]);
		if (tap)
			break;
	}

out:
	return tap;
}

/*
 * The net_device is going away, give up the reference
 * that it holds on the queue (all the queues one day)
 * and safely set the pointer from the queues to NULL.
 * that it holds on all queues and safely set the pointer
 * from the queues to NULL.
 */
static void macvtap_del_queues(struct net_device *dev)
{
	struct macvlan_dev *vlan = netdev_priv(dev);
	struct macvtap_queue *q;
	struct macvtap_queue *q, *qlist[MAX_MACVTAP_QUEUES];
	int i, j = 0;

	/* macvtap_put_queue can free some slots, so go through all slots */
	spin_lock(&macvtap_lock);
	q = rcu_dereference(vlan->tap);
	if (!q) {
		spin_unlock(&macvtap_lock);
		return;
	}

	rcu_assign_pointer(vlan->tap, NULL);
	for (i = 0; i < MAX_MACVTAP_QUEUES && vlan->numvtaps; i++) {
		q = rcu_dereference(vlan->taps[i]);
		if (q) {
			qlist[j++] = q;
			rcu_assign_pointer(vlan->taps[i], NULL);
			rcu_assign_pointer(q->vlan, NULL);
			vlan->numvtaps--;
		}
	}
	BUG_ON(vlan->numvtaps != 0);
	spin_unlock(&macvtap_lock);

	synchronize_rcu();
	sock_put(&q->sk);

	for (--j; j >= 0; j--)
		sock_put(&qlist[j]->sk);
}

/*
+8 −1
Original line number Diff line number Diff line
@@ -40,6 +40,12 @@ struct macvlan_rx_stats {
	unsigned long		rx_errors;
};

/*
 * Maximum times a macvtap device can be opened. This can be used to
 * configure the number of receive queue, e.g. for multiqueue virtio.
 */
#define MAX_MACVTAP_QUEUES	(NR_CPUS < 16 ? NR_CPUS : 16)

struct macvlan_dev {
	struct net_device	*dev;
	struct list_head	list;
@@ -50,7 +56,8 @@ struct macvlan_dev {
	enum macvlan_mode	mode;
	int (*receive)(struct sk_buff *skb);
	int (*forward)(struct net_device *dev, struct sk_buff *skb);
	struct macvtap_queue	*tap;
	struct macvtap_queue	*taps[MAX_MACVTAP_QUEUES];
	int			numvtaps;
};

static inline void macvlan_count_rx(const struct macvlan_dev *vlan,