[PATCH] netif.h: Document xen-net{back, front} multi-queue feature

["Andrew J. Bennieston" <andrew.bennieston@citrix.com>]

From: "Andrew J. Bennieston" <andrew.bennieston@citrix.com>

Document the multi-queue feature in terms of XenStore keys to be written
by the backend and by the frontend.

Signed-off-by: Andrew J. Bennieston <andrew.bennieston@citrix.com>
---
 xen/include/public/io/netif.h |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index d7fb771..90be2fc 100644
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -69,6 +69,27 @@
  */
 
 /*
+ * Multiple transmit and receive queues:
+ * If supported, the backend will write "multi-queue-max-queues" and set its
+ * value to the maximum supported number of queues.
+ * Frontends that are aware of this feature and wish to use it can write the
+ * key "multi-queue-num-queues", set to the number they wish to use.
+ *
+ * Queues replicate the shared rings and event channels, and
+ * "feature-split-event-channels" is required when using multiple queues.
+ *
+ * For frontends requesting just one queue, the usual event-channel and
+ * ring-ref keys are written as before, simplifying the backend processing
+ * to avoid distinguishing between a frontend that doesn't understand the
+ * multi-queue feature, and one that does, but requested only one queue.
+ *
+ * Frontends requesting two or more queues must not write the toplevel
+ * event-channel and ring-ref keys, instead writing them under sub-keys having
+ * the name "queue-N" where N is the integer ID of the queue for which those
+ * keys belong. Queues are indexed from zero.
+ */
+
+/*
  * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
  * offload off or on. If it is missing then the feature is assumed to be on.
  * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum
-- 
1.7.10.4