Merge branch 'xen-netback'

David Vrabel says:

====================
xen-netback: guest Rx queue drain and stall fixes

This series fixes two critical xen-netback bugs.

1. Netback may consume all of host memory by queuing an unlimited
   number of skb on the internal guest Rx queue.  This behaviour is
   guest triggerable.

2. Carrier flapping under high traffic rates which reduces
   performance.

The first patch is a prerequite.  Removing support for frontends with
feature-rx-notify makes it easier to reason about the correctness of
netback since it no longer has to support this outdated and broken
mode.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 59 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index f379689dde30..895fe84011e7 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -43,6 +43,9 @@
 #define XENVIF_QUEUE_LENGTH 32
 #define XENVIF_NAPI_WEIGHT  64
 
+/* Number of bytes allowed on the internal guest Rx queue. */
+#define XENVIF_RX_QUEUE_BYTES (XEN_NETIF_RX_RING_SIZE/2 * PAGE_SIZE)
+
 /* This function is used to set SKBTX_DEV_ZEROCOPY as well as
  * increasing the inflight counter. We need to increase the inflight
  * counter because core driver calls into xenvif_zerocopy_callback
@@ -60,20 +63,11 @@ void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
 	atomic_dec(&queue->inflight_packets);
 }
 
-static inline void xenvif_stop_queue(struct xenvif_queue *queue)
-{
-	struct net_device *dev = queue->vif->dev;
-
-	if (!queue->vif->can_queue)
-		return;
-
-	netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
-}
-
 int xenvif_schedulable(struct xenvif *vif)
 {
 	return netif_running(vif->dev) &&
-		test_bit(VIF_STATUS_CONNECTED, &vif->status);
+		test_bit(VIF_STATUS_CONNECTED, &vif->status) &&
+		!vif->disabled;
 }
 
 static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
@@ -114,16 +108,7 @@ int xenvif_poll(struct napi_struct *napi, int budget)
 static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
 {
 	struct xenvif_queue *queue = dev_id;
-	struct netdev_queue *net_queue =
-		netdev_get_tx_queue(queue->vif->dev, queue->id);
 
-	/* QUEUE_STATUS_RX_PURGE_EVENT is only set if either QDisc was off OR
-	 * the carrier went down and this queue was previously blocked
-	 */
-	if (unlikely(netif_tx_queue_stopped(net_queue) ||
-		     (!netif_carrier_ok(queue->vif->dev) &&
-		      test_bit(QUEUE_STATUS_RX_STALLED, &queue->status))))
-		set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
 	xenvif_kick_thread(queue);
 
 	return IRQ_HANDLED;
@@ -151,24 +136,13 @@ void xenvif_wake_queue(struct xenvif_queue *queue)
 	netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
 }
 
-/* Callback to wake the queue's thread and turn the carrier off on timeout */
-static void xenvif_rx_stalled(unsigned long data)
-{
-	struct xenvif_queue *queue = (struct xenvif_queue *)data;
-
-	if (xenvif_queue_stopped(queue)) {
-		set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
-		xenvif_kick_thread(queue);
-	}
-}
-
 static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct xenvif *vif = netdev_priv(dev);
 	struct xenvif_queue *queue = NULL;
 	unsigned int num_queues = vif->num_queues;
 	u16 index;
-	int min_slots_needed;
+	struct xenvif_rx_cb *cb;
 
 	BUG_ON(skb->dev != dev);
 
@@ -191,30 +165,10 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	    !xenvif_schedulable(vif))
 		goto drop;
 
-	/* At best we'll need one slot for the header and one for each
-	 * frag.
-	 */
-	min_slots_needed = 1 + skb_shinfo(skb)->nr_frags;
-
-	/* If the skb is GSO then we'll also need an extra slot for the
-	 * metadata.
-	 */
-	if (skb_is_gso(skb))
-		min_slots_needed++;
+	cb = XENVIF_RX_CB(skb);
+	cb->expires = jiffies + rx_drain_timeout_jiffies;
 
-	/* If the skb can't possibly fit in the remaining slots
-	 * then turn off the queue to give the ring a chance to
-	 * drain.
-	 */
-	if (!xenvif_rx_ring_slots_available(queue, min_slots_needed)) {
-		queue->rx_stalled.function = xenvif_rx_stalled;
-		queue->rx_stalled.data = (unsigned long)queue;
-		xenvif_stop_queue(queue);
-		mod_timer(&queue->rx_stalled,
-			  jiffies + rx_drain_timeout_jiffies);
-	}
-
-	skb_queue_tail(&queue->rx_queue, skb);
+	xenvif_rx_queue_tail(queue, skb);
 	xenvif_kick_thread(queue);
 
 	return NETDEV_TX_OK;
@@ -465,6 +419,8 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	vif->queues = NULL;
 	vif->num_queues = 0;
 
+	spin_lock_init(&vif->lock);
+
 	dev->netdev_ops	= &xenvif_netdev_ops;
 	dev->hw_features = NETIF_F_SG |
 		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
@@ -508,6 +464,8 @@ int xenvif_init_queue(struct xenvif_queue *queue)
 	init_timer(&queue->credit_timeout);
 	queue->credit_window_start = get_jiffies_64();
 
+	queue->rx_queue_max = XENVIF_RX_QUEUE_BYTES;
+
 	skb_queue_head_init(&queue->rx_queue);
 	skb_queue_head_init(&queue->tx_queue);
 
@@ -539,8 +497,6 @@ int xenvif_init_queue(struct xenvif_queue *queue)
 		queue->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
 	}
 
-	init_timer(&queue->rx_stalled);
-
 	return 0;
 }
 
@@ -551,7 +507,6 @@ void xenvif_carrier_on(struct xenvif *vif)
 		dev_set_mtu(vif->dev, ETH_DATA_LEN);
 	netdev_update_features(vif->dev);
 	set_bit(VIF_STATUS_CONNECTED, &vif->status);
-	netif_carrier_on(vif->dev);
 	if (netif_running(vif->dev))
 		xenvif_up(vif);
 	rtnl_unlock();
@@ -611,6 +566,8 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
 		disable_irq(queue->rx_irq);
 	}
 
+	queue->stalled = true;
+
 	task = kthread_create(xenvif_kthread_guest_rx,
 			      (void *)queue, "%s-guest-rx", queue->name);
 	if (IS_ERR(task)) {
@@ -674,7 +631,6 @@ void xenvif_disconnect(struct xenvif *vif)
 		netif_napi_del(&queue->napi);
 
 		if (queue->task) {
-			del_timer_sync(&queue->rx_stalled);
 			kthread_stop(queue->task);
 			queue->task = NULL;
 		}