net: sched: mq: add simple offload notification

mq offload is trivial, we just need to let the device know
that the root qdisc is mq.  Alternative approach would be
to export qdisc_lookup() and make drivers check the root
type themselves, but notification via ndo_setup_tc is more
in line with other qdiscs.

Note that mq doesn't hold any stats on it's own, it just
adds up stats of its children.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -791,6 +791,7 @@ enum tc_setup_type {
 	TC_SETUP_QDISC_CBS,
 	TC_SETUP_QDISC_RED,
 	TC_SETUP_QDISC_PRIO,
+	TC_SETUP_QDISC_MQ,
 };
 
 /* These structures hold the attributes of bpf state that are being passed

include/net/pkt_cls.h

@@ -778,6 +778,16 @@ struct tc_qopt_offload_stats {
 	struct gnet_stats_queue *qstats;
 };
 
+enum tc_mq_command {
+	TC_MQ_CREATE,
+	TC_MQ_DESTROY,
+};
+
+struct tc_mq_qopt_offload {
+	enum tc_mq_command command;
+	u32 handle;
+};
+
 enum tc_red_command {
 	TC_RED_REPLACE,
 	TC_RED_DESTROY,

net/sched/sch_mq.c

@@ -16,6 +16,7 @@
 #include <linux/errno.h>
 #include <linux/skbuff.h>
 #include <net/netlink.h>
+#include <net/pkt_cls.h>
 #include <net/pkt_sched.h>
 #include <net/sch_generic.h>
 
@@ -23,12 +24,28 @@ struct mq_sched {
 	struct Qdisc		**qdiscs;
 };
 
+static int mq_offload(struct Qdisc *sch, enum tc_mq_command cmd)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct tc_mq_qopt_offload opt = {
+		.command = cmd,
+		.handle = sch->handle,
+	};
+
+	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
+		return -EOPNOTSUPP;
+
+	return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_MQ, &opt);
+}
+
 static void mq_destroy(struct Qdisc *sch)
 {
 	struct net_device *dev = qdisc_dev(sch);
 	struct mq_sched *priv = qdisc_priv(sch);
 	unsigned int ntx;
 
+	mq_offload(sch, TC_MQ_DESTROY);
+
 	if (!priv->qdiscs)
 		return;
 	for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
@@ -70,6 +87,8 @@ static int mq_init(struct Qdisc *sch, struct nlattr *opt,
 	}
 
 	sch->flags |= TCQ_F_MQROOT;
+
+	mq_offload(sch, TC_MQ_CREATE);
 	return 0;
 }