From: Andrew J. Bennieston Date: Wed, 4 Jun 2014 09:30:46 +0000 (+0100) Subject: xen-net{back, front}: Document multi-queue feature in netif.h X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=a2deb8b1e7a403fd63e08f87eb95217dd983e0d3;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git xen-net{back, front}: Document multi-queue feature in netif.h 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 Acked-by: Wei Liu Acked-by: Ian Campbell Reviewed-by: David Vrabel Signed-off-by: David S. Miller --- diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h index c50061db6098..70054cc0708d 100644 --- a/include/xen/interface/io/netif.h +++ b/include/xen/interface/io/netif.h @@ -50,6 +50,59 @@ * node as before. */ +/* + * Multiple transmit and receive queues: + * If supported, the backend will write the key "multi-queue-max-queues" to + * the directory for that vif, 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, which + * must be greater than zero, and no more than the value reported by the backend + * in "multi-queue-max-queues". + * + * Queues replicate the shared rings and event channels. + * "feature-split-event-channels" may optionally be used when using + * multiple queues, but is not mandatory. + * + * 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 those keys 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. For example, a frontend with two queues and split + * event channels must write the following set of queue-related keys: + * + * /local/domain/1/device/vif/0/multi-queue-num-queues = "2" + * /local/domain/1/device/vif/0/queue-0 = "" + * /local/domain/1/device/vif/0/queue-0/tx-ring-ref = "" + * /local/domain/1/device/vif/0/queue-0/rx-ring-ref = "" + * /local/domain/1/device/vif/0/queue-0/event-channel-tx = "" + * /local/domain/1/device/vif/0/queue-0/event-channel-rx = "" + * /local/domain/1/device/vif/0/queue-1 = "" + * /local/domain/1/device/vif/0/queue-1/tx-ring-ref = "" + * /local/domain/1/device/vif/0/queue-1/rx-ring-ref = "