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[Xen-devel] [PATCH net-next 2/2] xen-netfront: split event channels feature support



This patch adds a new feature called feature-split-event-channels for
netfront, enabling it to handle TX and RX events separately.

If netback does not support this feature, it falls back to use single event
channel.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 drivers/net/xen-netfront.c |  181 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 152 insertions(+), 29 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 5770e3b..716b2bd 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -85,7 +85,15 @@ struct netfront_info {
 
        struct napi_struct napi;
 
-       unsigned int evtchn;
+       /* Split event channels support, tx_* == rx_* when using
+        * single event channel.
+        */
+       unsigned int tx_evtchn, rx_evtchn;
+       unsigned int tx_irq, rx_irq;
+       /* Only used when split event channels support is enabled */
+       char tx_irq_name[IFNAMSIZ+4]; /* DEVNAME-tx */
+       char rx_irq_name[IFNAMSIZ+4]; /* DEVNAME-rx */
+
        struct xenbus_device *xbdev;
 
        spinlock_t   tx_lock;
@@ -330,7 +338,7 @@ no_skb:
  push:
        RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->rx, notify);
        if (notify)
-               notify_remote_via_irq(np->netdev->irq);
+               notify_remote_via_irq(np->rx_irq);
 }
 
 static int xennet_open(struct net_device *dev)
@@ -623,7 +631,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct 
net_device *dev)
 
        RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->tx, notify);
        if (notify)
-               notify_remote_via_irq(np->netdev->irq);
+               notify_remote_via_irq(np->tx_irq);
 
        u64_stats_update_begin(&stats->syncp);
        stats->tx_bytes += skb->len;
@@ -1254,23 +1262,35 @@ static int xennet_set_features(struct net_device *dev,
        return 0;
 }
 
-static irqreturn_t xennet_interrupt(int irq, void *dev_id)
+static irqreturn_t xennet_tx_interrupt(int irq, void *dev_id)
 {
-       struct net_device *dev = dev_id;
-       struct netfront_info *np = netdev_priv(dev);
+       struct netfront_info *np = dev_id;
+       struct net_device *dev = np->netdev;
        unsigned long flags;
 
        spin_lock_irqsave(&np->tx_lock, flags);
+       xennet_tx_buf_gc(dev);
+       spin_unlock_irqrestore(&np->tx_lock, flags);
 
-       if (likely(netif_carrier_ok(dev))) {
-               xennet_tx_buf_gc(dev);
-               /* Under tx_lock: protects access to rx shared-ring indexes. */
-               if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
+       return IRQ_HANDLED;
+}
+
+static irqreturn_t xennet_rx_interrupt(int irq, void *dev_id)
+{
+       struct netfront_info *np = dev_id;
+       struct net_device *dev = np->netdev;
+
+       if (likely(netif_carrier_ok(dev) &&
+                  RING_HAS_UNCONSUMED_RESPONSES(&np->rx)))
                        napi_schedule(&np->napi);
-       }
 
-       spin_unlock_irqrestore(&np->tx_lock, flags);
+       return IRQ_HANDLED;
+}
 
+static irqreturn_t xennet_interrupt(int irq, void *dev_id)
+{
+       xennet_tx_interrupt(irq, dev_id);
+       xennet_rx_interrupt(irq, dev_id);
        return IRQ_HANDLED;
 }
 
@@ -1451,9 +1471,14 @@ static void xennet_disconnect_backend(struct 
netfront_info *info)
        spin_unlock_irq(&info->tx_lock);
        spin_unlock_bh(&info->rx_lock);
 
-       if (info->netdev->irq)
-               unbind_from_irqhandler(info->netdev->irq, info->netdev);
-       info->evtchn = info->netdev->irq = 0;
+       if (info->tx_irq && (info->tx_irq == info->rx_irq))
+               unbind_from_irqhandler(info->tx_irq, info);
+       if (info->tx_irq && (info->tx_irq != info->rx_irq)) {
+               unbind_from_irqhandler(info->tx_irq, info);
+               unbind_from_irqhandler(info->rx_irq, info);
+       }
+       info->tx_evtchn = info->rx_evtchn = 0;
+       info->tx_irq = info->rx_irq = 0;
 
        /* End access and free the pages */
        xennet_end_access(info->tx_ring_ref, info->tx.sring);
@@ -1503,12 +1528,90 @@ static int xen_net_read_mac(struct xenbus_device *dev, 
u8 mac[])
        return 0;
 }
 
+static int setup_netfront_single(struct netfront_info *info)
+{
+       int err;
+
+       err = xenbus_alloc_evtchn(info->xbdev, &info->tx_evtchn);
+       if (err < 0)
+               goto fail;
+
+       err = bind_evtchn_to_irqhandler(info->tx_evtchn,
+                                       xennet_interrupt,
+                                       0, info->netdev->name, info);
+       if (err < 0)
+               goto bind_fail;
+       info->rx_evtchn = info->tx_evtchn;
+       info->rx_irq = info->tx_irq = err;
+       dev_info(&info->xbdev->dev,
+                "single event channel, evtchn = %d, irq = %d\n",
+                info->tx_evtchn, info->tx_irq);
+
+       return 0;
+
+bind_fail:
+       xenbus_free_evtchn(info->xbdev, info->tx_evtchn);
+       info->tx_evtchn = 0;
+fail:
+       return err;
+}
+
+static int setup_netfront_split(struct netfront_info *info)
+{
+       int err;
+
+       err = xenbus_alloc_evtchn(info->xbdev, &info->tx_evtchn);
+       if (err < 0)
+               goto fail;
+       err = xenbus_alloc_evtchn(info->xbdev, &info->rx_evtchn);
+       if (err < 0)
+               goto alloc_rx_evtchn_fail;
+
+       snprintf(info->tx_irq_name, sizeof(info->tx_irq_name),
+                "%s-tx", info->netdev->name);
+       err = bind_evtchn_to_irqhandler(info->tx_evtchn,
+                                       xennet_tx_interrupt,
+                                       0, info->tx_irq_name, info);
+       if (err < 0)
+               goto bind_tx_fail;
+       info->tx_irq = err;
+
+       snprintf(info->rx_irq_name, sizeof(info->rx_irq_name),
+                "%s-rx", info->netdev->name);
+       err = bind_evtchn_to_irqhandler(info->rx_evtchn,
+                                       xennet_rx_interrupt,
+                                       0, info->rx_irq_name, info);
+       if (err < 0)
+               goto bind_rx_fail;
+       info->rx_irq = err;
+
+       dev_info(&info->xbdev->dev,
+                "split event channels, tx_evtchn/irq = %d/%d, rx_evtchn/irq = 
%d/%d",
+                info->tx_evtchn, info->tx_irq,
+                info->rx_evtchn, info->rx_irq);
+
+       return 0;
+
+bind_rx_fail:
+       unbind_from_irqhandler(info->tx_irq, info);
+       info->tx_irq = 0;
+bind_tx_fail:
+       xenbus_free_evtchn(info->xbdev, info->rx_evtchn);
+       info->rx_evtchn = 0;
+alloc_rx_evtchn_fail:
+       xenbus_free_evtchn(info->xbdev, info->tx_evtchn);
+       info->tx_evtchn = 0;
+fail:
+       return err;
+}
+
 static int setup_netfront(struct xenbus_device *dev, struct netfront_info 
*info)
 {
        struct xen_netif_tx_sring *txs;
        struct xen_netif_rx_sring *rxs;
        int err;
        struct net_device *netdev = info->netdev;
+       unsigned int feature_split_evtchn;
 
        info->tx_ring_ref = GRANT_INVALID_REF;
        info->rx_ring_ref = GRANT_INVALID_REF;
@@ -1516,6 +1619,12 @@ static int setup_netfront(struct xenbus_device *dev, 
struct netfront_info *info)
        info->tx.sring = NULL;
        netdev->irq = 0;
 
+       err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+                          "feature-split-event-channels", "%u",
+                          &feature_split_evtchn);
+       if (err < 0)
+               feature_split_evtchn = 0;
+
        err = xen_net_read_mac(dev, netdev->dev_addr);
        if (err) {
                xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
@@ -1550,22 +1659,18 @@ static int setup_netfront(struct xenbus_device *dev, 
struct netfront_info *info)
                goto grant_rx_ring_fail;
        info->rx_ring_ref = err;
 
-       err = xenbus_alloc_evtchn(dev, &info->evtchn);
+       if (feature_split_evtchn)
+               err = setup_netfront_split(info);
+       else
+               err = setup_netfront_single(info);
        if (err)
                goto alloc_evtchn_fail;
 
-       err = bind_evtchn_to_irqhandler(info->evtchn, xennet_interrupt,
-                                       0, netdev->name, netdev);
-       if (err < 0)
-               goto bind_fail;
-       netdev->irq = err;
        return 0;
 
        /* If we fail to setup netfront, it is safe to just revoke access to
         * granted pages because backend is not accessing it at this point.
         */
-bind_fail:
-       xenbus_free_evtchn(dev, info->evtchn);
 alloc_evtchn_fail:
        gnttab_end_foreign_access_ref(info->rx_ring_ref, 0);
 grant_rx_ring_fail:
@@ -1610,11 +1715,27 @@ again:
                message = "writing rx ring-ref";
                goto abort_transaction;
        }
-       err = xenbus_printf(xbt, dev->nodename,
-                           "event-channel", "%u", info->evtchn);
-       if (err) {
-               message = "writing event-channel";
-               goto abort_transaction;
+
+       if (info->tx_evtchn == info->rx_evtchn) {
+               err = xenbus_printf(xbt, dev->nodename,
+                                   "event-channel", "%u", info->tx_evtchn);
+               if (err) {
+                       message = "writing event-channel";
+                       goto abort_transaction;
+               }
+       } else {
+               err = xenbus_printf(xbt, dev->nodename,
+                                   "event-channel-tx", "%u", info->tx_evtchn);
+               if (err) {
+                       message = "writing event-channel-tx";
+                       goto abort_transaction;
+               }
+               err = xenbus_printf(xbt, dev->nodename,
+                                   "event-channel-rx", "%u", info->rx_evtchn);
+               if (err) {
+                       message = "writing event-channel-rx";
+                       goto abort_transaction;
+               }
        }
 
        err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u",
@@ -1727,7 +1848,9 @@ static int xennet_connect(struct net_device *dev)
         * packets.
         */
        netif_carrier_on(np->netdev);
-       notify_remote_via_irq(np->netdev->irq);
+       notify_remote_via_irq(np->tx_irq);
+       if (np->tx_irq != np->rx_irq)
+               notify_remote_via_irq(np->rx_irq);
        xennet_tx_buf_gc(dev);
        xennet_alloc_rx_buffers(dev);
 
-- 
1.7.10.4


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