Commit edd025ca authored by Edward Cree's avatar Edward Cree Committed by David S. Miller
Browse files

sfc: document TC-to-EF100-MAE action translation concepts 



Includes an explanation of the lifetime of the 'cursor' action-set `act`.

Signed-off-by: default avatarEdward Cree <ecree.xilinx@gmail.com>
Reviewed-by: default avatarSimon Horman <simon.horman@corigine.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 37018b5a

drivers/net/ethernet/sfc/tc.c

+25 −1
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ static const struct rhashtable_params efx_tc_match_action_ht_params = { 
static void efx_tc_free_action_set(struct efx_nic *efx,

				   struct efx_tc_action_set *act, bool in_hw)

{

	/* Failure paths calling this on the 'running action' set in_hw=false,

	/* Failure paths calling this on the 'cursor' action set in_hw=false,

	 * because if the alloc had succeeded we'd've put it in acts.list and

	 * not still have it in act.

	 */
@@ -407,6 +407,30 @@ static int efx_tc_flower_replace(struct efx_nic *efx, 
		goto release;

	}



	/**

	 * DOC: TC action translation

	 *

	 * Actions in TC are sequential and cumulative, with delivery actions

	 * potentially anywhere in the order.  The EF100 MAE, however, takes

	 * an 'action set list' consisting of 'action sets', each of which is

	 * applied to the _original_ packet, and consists of a set of optional

	 * actions in a fixed order with delivery at the end.

	 * To translate between these two models, we maintain a 'cursor', @act,

	 * which describes the cumulative effect of all the packet-mutating

	 * actions encountered so far; on handling a delivery (mirred or drop)

	 * action, once the action-set has been inserted into hardware, we

	 * append @act to the action-set list (@rule->acts); if this is a pipe

	 * action (mirred mirror) we then allocate a new @act with a copy of

	 * the cursor state _before_ the delivery action, otherwise we set @act

	 * to %NULL.

	 * This ensures that every allocated action-set is either attached to

	 * @rule->acts or pointed to by @act (and never both), and that only

	 * those action-sets in @rule->acts exist in hardware.  Consequently,

	 * in the failure path, @act only needs to be freed in memory, whereas

	 * for @rule->acts we remove each action-set from hardware before

	 * freeing it (efx_tc_free_action_set_list()), even if the action-set

	 * list itself is not in hardware.

	 */

	flow_action_for_each(i, fa, &fr->action) {

		struct efx_tc_action_set save;

		u16 tci;