xen-netback: split event channels support for Xen backend driver

Netback and netfront only use one event channel to do TX / RX notification,
which may cause unnecessary wake-up of processing routines. This patch adds a
new feature called feature-split-event-channels to netback, enabling it to
handle TX and RX events separately.

Netback will use tx_irq to notify guest for TX completion, rx_irq for RX
notification.

If frontend doesn't support this feature, tx_irq equals to rx_irq.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 70 insertions, 15 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 82202c2b1bd1..087d2db0389d 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -60,21 +60,39 @@ static int xenvif_rx_schedulable(struct xenvif *vif)
         return xenvif_schedulable(vif) && !xen_netbk_rx_ring_full(vif);
 }
 
-static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
+static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
 {
         struct xenvif *vif = dev_id;
 
         if (vif->netbk == NULL)
-                return IRQ_NONE;
+                return IRQ_HANDLED;
 
         xen_netbk_schedule_xenvif(vif);
 
+        return IRQ_HANDLED;
+}
+
+static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
+{
+        struct xenvif *vif = dev_id;
+
+        if (vif->netbk == NULL)
+                return IRQ_HANDLED;
+
         if (xenvif_rx_schedulable(vif))
                 netif_wake_queue(vif->dev);
 
         return IRQ_HANDLED;
 }
 
+static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
+{
+        xenvif_tx_interrupt(irq, dev_id);
+        xenvif_rx_interrupt(irq, dev_id);
+
+        return IRQ_HANDLED;
+}
+
 static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct xenvif *vif = netdev_priv(dev);
@@ -125,13 +143,17 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
 static void xenvif_up(struct xenvif *vif)
 {
         xen_netbk_add_xenvif(vif);
-        enable_irq(vif->irq);
+        enable_irq(vif->tx_irq);
+        if (vif->tx_irq != vif->rx_irq)
+                enable_irq(vif->rx_irq);
         xen_netbk_check_rx_xenvif(vif);
 }
 
 static void xenvif_down(struct xenvif *vif)
 {
-        disable_irq(vif->irq);
+        disable_irq(vif->tx_irq);
+        if (vif->tx_irq != vif->rx_irq)
+                disable_irq(vif->rx_irq);
         del_timer_sync(&vif->credit_timeout);
         xen_netbk_deschedule_xenvif(vif);
         xen_netbk_remove_xenvif(vif);
@@ -308,12 +330,13 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 }
 
 int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
-                   unsigned long rx_ring_ref, unsigned int evtchn)
+                   unsigned long rx_ring_ref, unsigned int tx_evtchn,
+                   unsigned int rx_evtchn)
 {
         int err = -ENOMEM;
 
         /* Already connected through? */
-        if (vif->irq)
+        if (vif->tx_irq)
                 return 0;
 
         __module_get(THIS_MODULE);
@@ -322,13 +345,37 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
         if (err < 0)
                 goto err;
 
-        err = bind_interdomain_evtchn_to_irqhandler(
-                vif->domid, evtchn, xenvif_interrupt, 0,
-                vif->dev->name, vif);
-        if (err < 0)
-                goto err_unmap;
-        vif->irq = err;
-        disable_irq(vif->irq);
+        if (tx_evtchn == rx_evtchn) {
+                /* feature-split-event-channels == 0 */
+                err = bind_interdomain_evtchn_to_irqhandler(
+                        vif->domid, tx_evtchn, xenvif_interrupt, 0,
+                        vif->dev->name, vif);
+                if (err < 0)
+                        goto err_unmap;
+                vif->tx_irq = vif->rx_irq = err;
+                disable_irq(vif->tx_irq);
+        } else {
+                /* feature-split-event-channels == 1 */
+                snprintf(vif->tx_irq_name, sizeof(vif->tx_irq_name),
+                         "%s-tx", vif->dev->name);
+                err = bind_interdomain_evtchn_to_irqhandler(
+                        vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
+                        vif->tx_irq_name, vif);
+                if (err < 0)
+                        goto err_unmap;
+                vif->tx_irq = err;
+                disable_irq(vif->tx_irq);
+
+                snprintf(vif->rx_irq_name, sizeof(vif->rx_irq_name),
+                         "%s-rx", vif->dev->name);
+                err = bind_interdomain_evtchn_to_irqhandler(
+                        vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
+                        vif->rx_irq_name, vif);
+                if (err < 0)
+                        goto err_tx_unbind;
+                vif->rx_irq = err;
+                disable_irq(vif->rx_irq);
+        }
 
         xenvif_get(vif);
 
@@ -342,6 +389,9 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
         rtnl_unlock();
 
         return 0;
+err_tx_unbind:
+        unbind_from_irqhandler(vif->tx_irq, vif);
+        vif->tx_irq = 0;
 err_unmap:
         xen_netbk_unmap_frontend_rings(vif);
 err:
@@ -375,8 +425,13 @@ void xenvif_disconnect(struct xenvif *vif)
         atomic_dec(&vif->refcnt);
         wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
 
-        if (vif->irq) {
-                unbind_from_irqhandler(vif->irq, vif);
+        if (vif->tx_irq) {
+                if (vif->tx_irq == vif->rx_irq)
+                        unbind_from_irqhandler(vif->tx_irq, vif);
+                else {
+                        unbind_from_irqhandler(vif->tx_irq, vif);
+                        unbind_from_irqhandler(vif->rx_irq, vif);
+                }
                 /* vif->irq is valid, we had a module_get in
                  * xenvif_connect.
                  */