From: Edward Cree <ecree@solarflare.com>
Date: Wed, 20 May 2020 19:18:10 +0100
Subject: net: flow_offload: simplify hw stats check handling
Patch-mainline: v5.8-rc1
Git-commit: 060b6381efe58478e1d7dfff7a1e76a73a6377db
References: bsc#1176774

Make FLOW_ACTION_HW_STATS_DONT_CARE be all bits, rather than none, so that
 drivers and __flow_action_hw_stats_check can use simple bitwise checks.

Pre-fill all actions with DONT_CARE in flow_rule_alloc(), rather than
 relying on implicit semantics of zero from kzalloc, so that callers which
 don't configure action stats themselves (i.e. netfilter) get the correct
 behaviour by default.

Only the kernel's internal API semantics change; the TC uAPI is unaffected.

v4: move DONT_CARE setting to flow_rule_alloc() for robustness and simplicity.

v3: set DONT_CARE in nft and ct offload.

v2: rebased on net-next, removed RFC tags.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_flower.c |    8 ++++----
 include/net/flow_offload.h                            |   11 +++++++----
 net/core/flow_offload.c                               |    6 ++++++
 3 files changed, 17 insertions(+), 8 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_flower.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_flower.c
@@ -30,14 +30,14 @@ static int mlxsw_sp_flower_parse_actions
 		return -EOPNOTSUPP;
 
 	act = flow_action_first_entry_get(flow_action);
-	if (act->hw_stats == FLOW_ACTION_HW_STATS_ANY ||
-	    act->hw_stats == FLOW_ACTION_HW_STATS_IMMEDIATE) {
+	if (act->hw_stats & FLOW_ACTION_HW_STATS_DISABLED) {
+		/* Nothing to do */
+	} else if (act->hw_stats & FLOW_ACTION_HW_STATS_IMMEDIATE) {
 		/* Count action is inserted first */
 		err = mlxsw_sp_acl_rulei_act_count(mlxsw_sp, rulei, extack);
 		if (err)
 			return err;
-	} else if (act->hw_stats != FLOW_ACTION_HW_STATS_DISABLED &&
-		   act->hw_stats != FLOW_ACTION_HW_STATS_DONT_CARE) {
+	} else {
 		NL_SET_ERR_MSG_MOD(extack, "Unsupported action HW stats type");
 		return -EOPNOTSUPP;
 	}
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -167,10 +167,11 @@ enum flow_action_hw_stats_bit {
 	FLOW_ACTION_HW_STATS_IMMEDIATE_BIT,
 	FLOW_ACTION_HW_STATS_DELAYED_BIT,
 	FLOW_ACTION_HW_STATS_DISABLED_BIT,
+
+	FLOW_ACTION_HW_STATS_NUM_BITS
 };
 
 enum flow_action_hw_stats {
-	FLOW_ACTION_HW_STATS_DONT_CARE = 0,
 	FLOW_ACTION_HW_STATS_IMMEDIATE =
 		BIT(FLOW_ACTION_HW_STATS_IMMEDIATE_BIT),
 	FLOW_ACTION_HW_STATS_DELAYED = BIT(FLOW_ACTION_HW_STATS_DELAYED_BIT),
@@ -178,6 +179,7 @@ enum flow_action_hw_stats {
 				   FLOW_ACTION_HW_STATS_DELAYED,
 	FLOW_ACTION_HW_STATS_DISABLED =
 		BIT(FLOW_ACTION_HW_STATS_DISABLED_BIT),
+	FLOW_ACTION_HW_STATS_DONT_CARE = BIT(FLOW_ACTION_HW_STATS_NUM_BITS) - 1,
 };
 
 typedef void (*action_destr)(void *priv);
@@ -329,11 +331,12 @@ __flow_action_hw_stats_check(const struc
 		return false;
 
 	action_entry = flow_action_first_entry_get(action);
-	if (action_entry->hw_stats == FLOW_ACTION_HW_STATS_DONT_CARE)
-		return true;
+
+	/* Zero is not a legal value for hw_stats, catch anyone passing it */
+	WARN_ON_ONCE(!action_entry->hw_stats);
 
 	if (!check_allow_bit &&
-	    action_entry->hw_stats != FLOW_ACTION_HW_STATS_ANY) {
+	    ~action_entry->hw_stats & FLOW_ACTION_HW_STATS_ANY) {
 		NL_SET_ERR_MSG_MOD(extack, "Driver supports only default HW stats type \"any\"");
 		return false;
 	} else if (check_allow_bit &&
--- a/net/core/flow_offload.c
+++ b/net/core/flow_offload.c
@@ -8,6 +8,7 @@
 struct flow_rule *flow_rule_alloc(unsigned int num_actions)
 {
 	struct flow_rule *rule;
+	int i;
 
 	rule = kzalloc(struct_size(rule, action.entries, num_actions),
 		       GFP_KERNEL);
@@ -15,6 +16,11 @@ struct flow_rule *flow_rule_alloc(unsign
 		return NULL;
 
 	rule->action.num_entries = num_actions;
+	/* Pre-fill each action hw_stats with DONT_CARE.
+	 * Caller can override this if it wants stats for a given action.
+	 */
+	for (i = 0; i < num_actions; i++)
+		rule->action.entries[i].hw_stats = FLOW_ACTION_HW_STATS_DONT_CARE;
 
 	return rule;
 }