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>

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 6102a6c59f4ef50a1867b5fd64dace788c209203..8a4d77ee9c5b61a312c3f2142ffa42fc0671e122 100644 (file)
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -57,8 +57,12 @@ struct xenvif {
 
        u8               fe_dev_addr[6];
 
-       /* Physical parameters of the comms window. */
-       unsigned int     irq;
+       /* When feature-split-event-channels = 0, tx_irq = rx_irq. */
+       unsigned int tx_irq;
+       unsigned int rx_irq;
+       /* Only used when feature-split-event-channels = 1 */
+       char tx_irq_name[IFNAMSIZ+4]; /* DEVNAME-tx */
+       char rx_irq_name[IFNAMSIZ+4]; /* DEVNAME-rx */
 
        /* List of frontends to notify after a batch of frames sent. */
        struct list_head notify_list;
@@ -113,7 +117,8 @@ struct xenvif *xenvif_alloc(struct device *parent,
                            unsigned int handle);
 
 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);
 void xenvif_disconnect(struct xenvif *vif);
 
 void xenvif_get(struct xenvif *vif);
@@ -158,4 +163,6 @@ void xenvif_carrier_off(struct xenvif *vif);
 /* Returns number of ring slots required to send an skb to the frontend */
 unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb);
 
+extern bool separate_tx_rx_irq;
+
 #endif /* __XEN_NETBACK__COMMON_H__ */

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 82202c2b1bd11a59c6175f3af393dff4060faa3f..087d2db0389d04efc3368a0ba48a925a3b070124 100644 (file)
--- 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.
                 */

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 2d9477fd900f1aff4ead55582e21225b14da1046..82576fffb4526a9964cd4f5074e77770bbb7373b 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -47,6 +47,13 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/page.h>
 
+/* Provide an option to disable split event channels at load time as
+ * event channels are limited resource. Split event channels are
+ * enabled by default.
+ */
+bool separate_tx_rx_irq = 1;
+module_param(separate_tx_rx_irq, bool, 0644);
+
 /*
  * This is the maximum slots a skb can have. If a guest sends a skb
  * which exceeds this limit it is considered malicious.
@@ -662,7 +669,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 {
        struct xenvif *vif = NULL, *tmp;
        s8 status;
-       u16 irq, flags;
+       u16 flags;
        struct xen_netif_rx_response *resp;
        struct sk_buff_head rxq;
        struct sk_buff *skb;
@@ -771,7 +778,6 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
                                         sco->meta_slots_used);
 
                RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret);
-               irq = vif->irq;
                if (ret && list_empty(&vif->notify_list))
                        list_add_tail(&vif->notify_list, &notify);
 
@@ -783,7 +789,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
        }
 
        list_for_each_entry_safe(vif, tmp, &notify, notify_list) {
-               notify_remote_via_irq(vif->irq);
+               notify_remote_via_irq(vif->rx_irq);
                list_del_init(&vif->notify_list);
        }
 
@@ -1762,7 +1768,7 @@ static void make_tx_response(struct xenvif *vif,
        vif->tx.rsp_prod_pvt = ++i;
        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->tx, notify);
        if (notify)
-               notify_remote_via_irq(vif->irq);
+               notify_remote_via_irq(vif->tx_irq);
 }
 
 static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index d230c145660c8fdf71a71b7ed72f14f1e9581f16..04bd860d16a9c29afb6458906529d3f38aa6d72f 100644 (file)
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -122,6 +122,16 @@ static int netback_probe(struct xenbus_device *dev,
                goto fail;
        }
 
+       /*
+        * Split event channels support, this is optional so it is not
+        * put inside the above loop.
+        */
+       err = xenbus_printf(XBT_NIL, dev->nodename,
+                           "feature-split-event-channels",
+                           "%u", separate_tx_rx_irq);
+       if (err)
+               pr_debug("Error writing feature-split-event-channels");
+
        err = xenbus_switch_state(dev, XenbusStateInitWait);
        if (err)
                goto fail;
@@ -393,21 +403,36 @@ static int connect_rings(struct backend_info *be)
        struct xenvif *vif = be->vif;
        struct xenbus_device *dev = be->dev;
        unsigned long tx_ring_ref, rx_ring_ref;
-       unsigned int evtchn, rx_copy;
+       unsigned int tx_evtchn, rx_evtchn, rx_copy;
        int err;
        int val;
 
        err = xenbus_gather(XBT_NIL, dev->otherend,
                            "tx-ring-ref", "%lu", &tx_ring_ref,
-                           "rx-ring-ref", "%lu", &rx_ring_ref,
-                           "event-channel", "%u", &evtchn, NULL);
+                           "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
        if (err) {
                xenbus_dev_fatal(dev, err,
-                                "reading %s/ring-ref and event-channel",
+                                "reading %s/ring-ref",
                                 dev->otherend);
                return err;
        }
 
+       /* Try split event channels first, then single event channel. */
+       err = xenbus_gather(XBT_NIL, dev->otherend,
+                           "event-channel-tx", "%u", &tx_evtchn,
+                           "event-channel-rx", "%u", &rx_evtchn, NULL);
+       if (err < 0) {
+               err = xenbus_scanf(XBT_NIL, dev->otherend,
+                                  "event-channel", "%u", &tx_evtchn);
+               if (err < 0) {
+                       xenbus_dev_fatal(dev, err,
+                                        "reading %s/event-channel(-tx/rx)",
+                                        dev->otherend);
+                       return err;
+               }
+               rx_evtchn = tx_evtchn;
+       }
+
        err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
                           &rx_copy);
        if (err == -ENOENT) {
@@ -454,11 +479,13 @@ static int connect_rings(struct backend_info *be)
        vif->csum = !val;
 
        /* Map the shared frame, irq etc. */
-       err = xenvif_connect(vif, tx_ring_ref, rx_ring_ref, evtchn);
+       err = xenvif_connect(vif, tx_ring_ref, rx_ring_ref,
+                            tx_evtchn, rx_evtchn);
        if (err) {
                xenbus_dev_fatal(dev, err,
-                                "mapping shared-frames %lu/%lu port %u",
-                                tx_ring_ref, rx_ring_ref, evtchn);
+                                "mapping shared-frames %lu/%lu port tx %u rx %u",
+                                tx_ring_ref, rx_ring_ref,
+                                tx_evtchn, rx_evtchn);
                return err;
        }
        return 0;