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[Xen-devel] [PATCH V6 net-next 5/5] xen-net{back, front}: Document multi-queue feature in netif.h

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

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@xxxxxxxxxx>
 include/xen/interface/io/netif.h |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
index c50061d..a375a75 100644
--- a/include/xen/interface/io/netif.h
+++ b/include/xen/interface/io/netif.h
@@ -51,6 +51,35 @@
+ * 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" may be used when using multiple queues.
+ * Each queue consists of one shared ring pair, i.e. there must be the same
+ * number of tx and rx rings.
+ *
+ * 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 (or event-channel-{tx,rx}) and {tx,rx}-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.
+ *
+ * Mapping of packets to queues is considered to be a function of the
+ * transmitting system (backend or frontend) and is not negotiated
+ * between the two. Guests are free to transmit packets on any queue
+ * they choose, provided it has been set up correctly.
+ */
  * "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

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