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, 10 insertions, 4 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 2d9477fd900f..82576fffb452 100644
--- 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,