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/xenbus.c b/drivers/net/xen-netback/xenbus.c
index d230c14..04bd860 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -122,6 +122,16 @@
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 @@
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 @@
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;