net/sched: mqprio: allow offloading drivers to request queue count validation

mqprio_parse_opt() proudly has a comment:

	/* If hardware offload is requested we will leave it to the device
	 * to either populate the queue counts itself or to validate the
	 * provided queue counts.
	 */

Unfortunately some device drivers did not get this memo, and don't
validate the queue counts, or populate them.

In case drivers don't want to populate the queue counts themselves, just
act upon the requested configuration, it makes sense to introduce a tc
capability, and make mqprio query it, so they don't have to do the
validation themselves.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/pkt_sched.h

@@ -160,6 +160,10 @@ struct tc_etf_qopt_offload {
 	s32 queue;
 };
 
+struct tc_mqprio_caps {
+	bool validate_queue_counts:1;
+};
+
 struct tc_mqprio_qopt_offload {
 	/* struct tc_mqprio_qopt must always be the first element */
 	struct tc_mqprio_qopt qopt;

net/sched/sch_mqprio.c

@@ -35,6 +35,35 @@ static bool intervals_overlap(int a, int b, int c, int d)
 	return left < right;
 }
 
+static int mqprio_validate_queue_counts(struct net_device *dev,
+					const struct tc_mqprio_qopt *qopt)
+{
+	int i, j;
+
+	for (i = 0; i < qopt->num_tc; i++) {
+		unsigned int last = qopt->offset[i] + qopt->count[i];
+
+		/* Verify the queue count is in tx range being equal to the
+		 * real_num_tx_queues indicates the last queue is in use.
+		 */
+		if (qopt->offset[i] >= dev->real_num_tx_queues ||
+		    !qopt->count[i] ||
+		    last > dev->real_num_tx_queues)
+			return -EINVAL;
+
+		/* Verify that the offset and counts do not overlap */
+		for (j = i + 1; j < qopt->num_tc; j++) {
+			if (intervals_overlap(qopt->offset[i], last,
+					      qopt->offset[j],
+					      qopt->offset[j] +
+					      qopt->count[j]))
+				return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static int mqprio_enable_offload(struct Qdisc *sch,
 				 const struct tc_mqprio_qopt *qopt)
 {
@@ -110,9 +139,10 @@ static void mqprio_destroy(struct Qdisc *sch)
 		netdev_set_num_tc(dev, 0);
 }
 
-static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
+static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt,
+			    const struct tc_mqprio_caps *caps)
 {
-	int i, j;
+	int i, err;
 
 	/* Verify num_tc is not out of max range */
 	if (qopt->num_tc > TC_MAX_QUEUE)
@@ -131,35 +161,24 @@ static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
 	if (qopt->hw > TC_MQPRIO_HW_OFFLOAD_MAX)
 		qopt->hw = TC_MQPRIO_HW_OFFLOAD_MAX;
 
-	/* If hardware offload is requested we will leave it to the device
-	 * to either populate the queue counts itself or to validate the
-	 * provided queue counts.  If ndo_setup_tc is not present then
-	 * hardware doesn't support offload and we should return an error.
+	/* If hardware offload is requested, we will leave 3 options to the
+	 * device driver:
+	 * - populate the queue counts itself (and ignore what was requested)
+	 * - validate the provided queue counts by itself (and apply them)
+	 * - request queue count validation here (and apply them)
 	 */
-	if (qopt->hw)
-		return dev->netdev_ops->ndo_setup_tc ? 0 : -EINVAL;
-
-	for (i = 0; i < qopt->num_tc; i++) {
-		unsigned int last = qopt->offset[i] + qopt->count[i];
-
-		/* Verify the queue count is in tx range being equal to the
-		 * real_num_tx_queues indicates the last queue is in use.
-		 */
-		if (qopt->offset[i] >= dev->real_num_tx_queues ||
-		    !qopt->count[i] ||
-		    last > dev->real_num_tx_queues)
-			return -EINVAL;
-
-		/* Verify that the offset and counts do not overlap */
-		for (j = i + 1; j < qopt->num_tc; j++) {
-			if (intervals_overlap(qopt->offset[i], last,
-					      qopt->offset[j],
-					      qopt->offset[j] +
-					      qopt->count[j]))
-				return -EINVAL;
-		}
+	if (!qopt->hw || caps->validate_queue_counts) {
+		err = mqprio_validate_queue_counts(dev, qopt);
+		if (err)
+			return err;
 	}
 
+	/* If ndo_setup_tc is not present then hardware doesn't support offload
+	 * and we should return an error.
+	 */
+	if (qopt->hw && !dev->netdev_ops->ndo_setup_tc)
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -254,6 +273,7 @@ static int mqprio_init(struct Qdisc *sch, struct nlattr *opt,
 	struct Qdisc *qdisc;
 	int i, err = -EOPNOTSUPP;
 	struct tc_mqprio_qopt *qopt = NULL;
+	struct tc_mqprio_caps caps;
 	int len;
 
 	BUILD_BUG_ON(TC_MAX_QUEUE != TC_QOPT_MAX_QUEUE);
@@ -272,8 +292,11 @@ static int mqprio_init(struct Qdisc *sch, struct nlattr *opt,
 	if (!opt || nla_len(opt) < sizeof(*qopt))
 		return -EINVAL;
 
+	qdisc_offload_query_caps(dev, TC_SETUP_QDISC_MQPRIO,
+				 &caps, sizeof(caps));
+
 	qopt = nla_data(opt);
-	if (mqprio_parse_opt(dev, qopt))
+	if (mqprio_parse_opt(dev, qopt, &caps))
 		return -EINVAL;
 
 	len = nla_len(opt) - NLA_ALIGN(sizeof(*qopt));