Merge branch 'taprio-auto-qmaxsdu-new-tx'

Vladimir Oltean says:

====================
taprio automatic queueMaxSDU and new TXQ selection procedure

This patch set addresses 2 design limitations in the taprio software scheduler:

1. Software scheduling fundamentally prioritizes traffic incorrectly,
   in a way which was inspired from Intel igb/igc drivers and does not
   follow the inputs user space gives (traffic classes and TC to TXQ
   mapping). Patch 05/15 handles this, 01/15 - 04/15 are preparations
   for this work.

2. Software scheduling assumes that the gate for a traffic class closes
   as soon as the next interval begins. But this isn't true.
   If consecutive schedule entries have that traffic class gate open,
   there is no "gate close" event and taprio should keep dequeuing from
   that TC without interruptions. Patches 06/15 - 15/15 handle this.
   Patch 10/15 is a generic Qdisc change required for this to work.

Future development directions which depend on this patch set are:

- Propagating the automatic queueMaxSDU calculation down to offloading
  device drivers, instead of letting them calculate this, as
  vsc9959_tas_guard_bands_update() does today.

- A software data path for tc-taprio with preemptible traffic and
  Hold/Release events.

v1 at:
https://patchwork.kernel.org/project/netdevbpf/cover/20230128010719.2182346-1-vladimir.oltean@nxp.com/
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -2810,6 +2810,22 @@ static int igb_offload_txtime(struct igb_adapter *adapter,
 	return 0;
 }
 
+static int igb_tc_query_caps(struct igb_adapter *adapter,
+			     struct tc_query_caps_base *base)
+{
+	switch (base->type) {
+	case TC_SETUP_QDISC_TAPRIO: {
+		struct tc_taprio_caps *caps = base->caps;
+
+		caps->broken_mqprio = true;
+
+		return 0;
+	}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static LIST_HEAD(igb_block_cb_list);
 
 static int igb_setup_tc(struct net_device *dev, enum tc_setup_type type,
@@ -2818,6 +2834,8 @@ static int igb_setup_tc(struct net_device *dev, enum tc_setup_type type,
 	struct igb_adapter *adapter = netdev_priv(dev);
 
 	switch (type) {
+	case TC_QUERY_CAPS:
+		return igb_tc_query_caps(adapter, type_data);
 	case TC_SETUP_QDISC_CBS:
 		return igb_offload_cbs(adapter, type_data);
 	case TC_SETUP_BLOCK:

drivers/net/ethernet/intel/igc/igc_main.c

@@ -6214,10 +6214,10 @@ static int igc_tc_query_caps(struct igc_adapter *adapter,
 	case TC_SETUP_QDISC_TAPRIO: {
 		struct tc_taprio_caps *caps = base->caps;
 
-		if (hw->mac.type != igc_i225)
-			return -EOPNOTSUPP;
+		caps->broken_mqprio = true;
 
-		caps->gate_mask_per_txq = true;
+		if (hw->mac.type == igc_i225)
+			caps->gate_mask_per_txq = true;
 
 		return 0;
 	}

include/net/pkt_sched.h

@@ -177,6 +177,11 @@ struct tc_mqprio_qopt_offload {
 struct tc_taprio_caps {
 	bool supports_queue_max_sdu:1;
 	bool gate_mask_per_txq:1;
+	/* Device expects lower TXQ numbers to have higher priority over higher
+	 * TXQs, regardless of their TC mapping. DO NOT USE FOR NEW DRIVERS,
+	 * INSTEAD ENFORCE A PROPER TC:TXQ MAPPING COMING FROM USER SPACE.
+	 */
+	bool broken_mqprio:1;
 };
 
 struct tc_taprio_sched_entry {

net/sched/sch_api.c

@@ -1282,12 +1282,6 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 	if (err)
 		goto err_out3;
 
-	if (ops->init) {
-		err = ops->init(sch, tca[TCA_OPTIONS], extack);
-		if (err != 0)
-			goto err_out5;
-	}
-
 	if (tca[TCA_STAB]) {
 		stab = qdisc_get_stab(tca[TCA_STAB], extack);
 		if (IS_ERR(stab)) {
@@ -1296,11 +1290,18 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 		}
 		rcu_assign_pointer(sch->stab, stab);
 	}
+
+	if (ops->init) {
+		err = ops->init(sch, tca[TCA_OPTIONS], extack);
+		if (err != 0)
+			goto err_out5;
+	}
+
 	if (tca[TCA_RATE]) {
 		err = -EOPNOTSUPP;
 		if (sch->flags & TCQ_F_MQROOT) {
 			NL_SET_ERR_MSG(extack, "Cannot attach rate estimator to a multi-queue root qdisc");
-			goto err_out4;
+			goto err_out5;
 		}
 
 		err = gen_new_estimator(&sch->bstats,
@@ -1311,7 +1312,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 					tca[TCA_RATE]);
 		if (err) {
 			NL_SET_ERR_MSG(extack, "Failed to generate new estimator");
-			goto err_out4;
+			goto err_out5;
 		}
 	}
 
@@ -1321,6 +1322,8 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 	return sch;
 
 err_out5:
+	qdisc_put_stab(rtnl_dereference(sch->stab));
+err_out4:
 	/* ops->init() failed, we call ->destroy() like qdisc_create_dflt() */
 	if (ops->destroy)
 		ops->destroy(sch);
@@ -1332,16 +1335,6 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 err_out:
 	*errp = err;
 	return NULL;
-
-err_out4:
-	/*
-	 * Any broken qdiscs that would require a ops->reset() here?
-	 * The qdisc was never in action so it shouldn't be necessary.
-	 */
-	qdisc_put_stab(rtnl_dereference(sch->stab));
-	if (ops->destroy)
-		ops->destroy(sch);
-	goto err_out3;
 }
 
 static int qdisc_change(struct Qdisc *sch, struct nlattr **tca,

net/sched/sch_taprio.c

@@ -29,6 +29,8 @@
 #include "sch_mqprio_lib.h"
 
 static LIST_HEAD(taprio_list);
+static struct static_key_false taprio_have_broken_mqprio;
+static struct static_key_false taprio_have_working_mqprio;
 
 #define TAPRIO_ALL_GATES_OPEN -1
 
@@ -37,15 +39,19 @@ static LIST_HEAD(taprio_list);
 #define TAPRIO_FLAGS_INVALID U32_MAX
 
 struct sched_entry {
-	struct list_head list;
-
-	/* The instant that this entry "closes" and the next one
-	 * should open, the qdisc will make some effort so that no
-	 * packet leaves after this time.
+	/* Durations between this GCL entry and the GCL entry where the
+	 * respective traffic class gate closes
 	 */
-	ktime_t close_time;
+	u64 gate_duration[TC_MAX_QUEUE];
+	atomic_t budget[TC_MAX_QUEUE];
+	/* The qdisc makes some effort so that no packet leaves
+	 * after this time
+	 */
+	ktime_t gate_close_time[TC_MAX_QUEUE];
+	struct list_head list;
+	/* Used to calculate when to advance the schedule */
+	ktime_t end_time;
 	ktime_t next_txtime;
-	atomic_t budget;
 	int index;
 	u32 gate_mask;
 	u32 interval;
@@ -53,10 +59,16 @@ struct sched_entry {
 };
 
 struct sched_gate_list {
+	/* Longest non-zero contiguous gate durations per traffic class,
+	 * or 0 if a traffic class gate never opens during the schedule.
+	 */
+	u64 max_open_gate_duration[TC_MAX_QUEUE];
+	u32 max_frm_len[TC_MAX_QUEUE]; /* for the fast path */
+	u32 max_sdu[TC_MAX_QUEUE]; /* for dump */
 	struct rcu_head rcu;
 	struct list_head entries;
 	size_t num_entries;
-	ktime_t cycle_close_time;
+	ktime_t cycle_end_time;
 	s64 cycle_time;
 	s64 cycle_time_extension;
 	s64 base_time;
@@ -69,6 +81,8 @@ struct taprio_sched {
 	enum tk_offsets tk_offset;
 	int clockid;
 	bool offloaded;
+	bool detected_mqprio;
+	bool broken_mqprio;
 	atomic64_t picos_per_byte; /* Using picoseconds because for 10Gbps+
 				    * speeds it's sub-nanoseconds per byte
 				    */
@@ -80,8 +94,8 @@ struct taprio_sched {
 	struct sched_gate_list __rcu *admin_sched;
 	struct hrtimer advance_timer;
 	struct list_head taprio_list;
-	u32 max_frm_len[TC_MAX_QUEUE]; /* for the fast path */
-	u32 max_sdu[TC_MAX_QUEUE]; /* for dump and offloading */
+	int cur_txq[TC_MAX_QUEUE];
+	u32 max_sdu[TC_MAX_QUEUE]; /* save info from the user */
 	u32 txtime_delay;
 };
 
@@ -90,6 +104,57 @@ struct __tc_taprio_qopt_offload {
 	struct tc_taprio_qopt_offload offload;
 };
 
+static void taprio_calculate_gate_durations(struct taprio_sched *q,
+					    struct sched_gate_list *sched)
+{
+	struct net_device *dev = qdisc_dev(q->root);
+	int num_tc = netdev_get_num_tc(dev);
+	struct sched_entry *entry, *cur;
+	int tc;
+
+	list_for_each_entry(entry, &sched->entries, list) {
+		u32 gates_still_open = entry->gate_mask;
+
+		/* For each traffic class, calculate each open gate duration,
+		 * starting at this schedule entry and ending at the schedule
+		 * entry containing a gate close event for that TC.
+		 */
+		cur = entry;
+
+		do {
+			if (!gates_still_open)
+				break;
+
+			for (tc = 0; tc < num_tc; tc++) {
+				if (!(gates_still_open & BIT(tc)))
+					continue;
+
+				if (cur->gate_mask & BIT(tc))
+					entry->gate_duration[tc] += cur->interval;
+				else
+					gates_still_open &= ~BIT(tc);
+			}
+
+			cur = list_next_entry_circular(cur, &sched->entries, list);
+		} while (cur != entry);
+
+		/* Keep track of the maximum gate duration for each traffic
+		 * class, taking care to not confuse a traffic class which is
+		 * temporarily closed with one that is always closed.
+		 */
+		for (tc = 0; tc < num_tc; tc++)
+			if (entry->gate_duration[tc] &&
+			    sched->max_open_gate_duration[tc] < entry->gate_duration[tc])
+				sched->max_open_gate_duration[tc] = entry->gate_duration[tc];
+	}
+}
+
+static bool taprio_entry_allows_tx(ktime_t skb_end_time,
+				   struct sched_entry *entry, int tc)
+{
+	return ktime_before(skb_end_time, entry->gate_close_time[tc]);
+}
+
 static ktime_t sched_base_time(const struct sched_gate_list *sched)
 {
 	if (!sched)
@@ -182,6 +247,55 @@ static int length_to_duration(struct taprio_sched *q, int len)
 	return div_u64(len * atomic64_read(&q->picos_per_byte), PSEC_PER_NSEC);
 }
 
+static int duration_to_length(struct taprio_sched *q, u64 duration)
+{
+	return div_u64(duration * PSEC_PER_NSEC, atomic64_read(&q->picos_per_byte));
+}
+
+/* Sets sched->max_sdu[] and sched->max_frm_len[] to the minimum between the
+ * q->max_sdu[] requested by the user and the max_sdu dynamically determined by
+ * the maximum open gate durations at the given link speed.
+ */
+static void taprio_update_queue_max_sdu(struct taprio_sched *q,
+					struct sched_gate_list *sched,
+					struct qdisc_size_table *stab)
+{
+	struct net_device *dev = qdisc_dev(q->root);
+	int num_tc = netdev_get_num_tc(dev);
+	u32 max_sdu_from_user;
+	u32 max_sdu_dynamic;
+	u32 max_sdu;
+	int tc;
+
+	for (tc = 0; tc < num_tc; tc++) {
+		max_sdu_from_user = q->max_sdu[tc] ?: U32_MAX;
+
+		/* TC gate never closes => keep the queueMaxSDU
+		 * selected by the user
+		 */
+		if (sched->max_open_gate_duration[tc] == sched->cycle_time) {
+			max_sdu_dynamic = U32_MAX;
+		} else {
+			u32 max_frm_len;
+
+			max_frm_len = duration_to_length(q, sched->max_open_gate_duration[tc]);
+			if (stab)
+				max_frm_len -= stab->szopts.overhead;
+			max_sdu_dynamic = max_frm_len - dev->hard_header_len;
+		}
+
+		max_sdu = min(max_sdu_dynamic, max_sdu_from_user);
+
+		if (max_sdu != U32_MAX) {
+			sched->max_frm_len[tc] = max_sdu + dev->hard_header_len;
+			sched->max_sdu[tc] = max_sdu;
+		} else {
+			sched->max_frm_len[tc] = U32_MAX; /* never oversized */
+			sched->max_sdu[tc] = 0;
+		}
+	}
+}
+
 /* Returns the entry corresponding to next available interval. If
  * validate_interval is set, it only validates whether the timestamp occurs
  * when the gate corresponding to the skb's traffic class is open.
@@ -415,14 +529,33 @@ static long get_packet_txtime(struct sk_buff *skb, struct Qdisc *sch)
 	return txtime;
 }
 
-static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
-			      struct Qdisc *child, struct sk_buff **to_free)
+/* Devices with full offload are expected to honor this in hardware */
+static bool taprio_skb_exceeds_queue_max_sdu(struct Qdisc *sch,
+					     struct sk_buff *skb)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
+	struct sched_gate_list *sched;
 	int prio = skb->priority;
+	bool exceeds = false;
 	u8 tc;
 
+	tc = netdev_get_prio_tc_map(dev, prio);
+
+	rcu_read_lock();
+	sched = rcu_dereference(q->oper_sched);
+	if (sched && skb->len > sched->max_frm_len[tc])
+		exceeds = true;
+	rcu_read_unlock();
+
+	return exceeds;
+}
+
+static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
+			      struct Qdisc *child, struct sk_buff **to_free)
+{
+	struct taprio_sched *q = qdisc_priv(sch);
+
 	/* sk_flags are only safe to use on full sockets. */
 	if (skb->sk && sk_fullsock(skb->sk) && sock_flag(skb->sk, SOCK_TXTIME)) {
 		if (!is_valid_interval(skb, sch))
@@ -433,17 +566,53 @@ static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
 			return qdisc_drop(skb, sch, to_free);
 	}
 
-	/* Devices with full offload are expected to honor this in hardware */
-	tc = netdev_get_prio_tc_map(dev, prio);
-	if (skb->len > q->max_frm_len[tc])
-		return qdisc_drop(skb, sch, to_free);
-
 	qdisc_qstats_backlog_inc(sch, skb);
 	sch->q.qlen++;
 
 	return qdisc_enqueue(skb, child, to_free);
 }
 
+static int taprio_enqueue_segmented(struct sk_buff *skb, struct Qdisc *sch,
+				    struct Qdisc *child,
+				    struct sk_buff **to_free)
+{
+	unsigned int slen = 0, numsegs = 0, len = qdisc_pkt_len(skb);
+	netdev_features_t features = netif_skb_features(skb);
+	struct sk_buff *segs, *nskb;
+	int ret;
+
+	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
+	if (IS_ERR_OR_NULL(segs))
+		return qdisc_drop(skb, sch, to_free);
+
+	skb_list_walk_safe(segs, segs, nskb) {
+		skb_mark_not_on_list(segs);
+		qdisc_skb_cb(segs)->pkt_len = segs->len;
+		slen += segs->len;
+
+		/* FIXME: we should be segmenting to a smaller size
+		 * rather than dropping these
+		 */
+		if (taprio_skb_exceeds_queue_max_sdu(sch, segs))
+			ret = qdisc_drop(segs, sch, to_free);
+		else
+			ret = taprio_enqueue_one(segs, sch, child, to_free);
+
+		if (ret != NET_XMIT_SUCCESS) {
+			if (net_xmit_drop_count(ret))
+				qdisc_qstats_drop(sch);
+		} else {
+			numsegs++;
+		}
+	}
+
+	if (numsegs > 1)
+		qdisc_tree_reduce_backlog(sch, 1 - numsegs, len - slen);
+	consume_skb(skb);
+
+	return numsegs > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
+}
+
 /* Will not be called in the full offload case, since the TX queues are
  * attached to the Qdisc created using qdisc_create_dflt()
  */
@@ -460,97 +629,190 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	if (unlikely(!child))
 		return qdisc_drop(skb, sch, to_free);
 
-	/* Large packets might not be transmitted when the transmission duration
-	 * exceeds any configured interval. Therefore, segment the skb into
-	 * smaller chunks. Drivers with full offload are expected to handle
-	 * this in hardware.
-	 */
-	if (skb_is_gso(skb)) {
-		unsigned int slen = 0, numsegs = 0, len = qdisc_pkt_len(skb);
-		netdev_features_t features = netif_skb_features(skb);
-		struct sk_buff *segs, *nskb;
-		int ret;
-
-		segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
-		if (IS_ERR_OR_NULL(segs))
-			return qdisc_drop(skb, sch, to_free);
+	if (taprio_skb_exceeds_queue_max_sdu(sch, skb)) {
+		/* Large packets might not be transmitted when the transmission
+		 * duration exceeds any configured interval. Therefore, segment
+		 * the skb into smaller chunks. Drivers with full offload are
+		 * expected to handle this in hardware.
+		 */
+		if (skb_is_gso(skb))
+			return taprio_enqueue_segmented(skb, sch, child,
+							to_free);
 
-		skb_list_walk_safe(segs, segs, nskb) {
-			skb_mark_not_on_list(segs);
-			qdisc_skb_cb(segs)->pkt_len = segs->len;
-			slen += segs->len;
+		return qdisc_drop(skb, sch, to_free);
+	}
 
-			ret = taprio_enqueue_one(segs, sch, child, to_free);
-			if (ret != NET_XMIT_SUCCESS) {
-				if (net_xmit_drop_count(ret))
-					qdisc_qstats_drop(sch);
-			} else {
-				numsegs++;
-			}
-		}
+	return taprio_enqueue_one(skb, sch, child, to_free);
+}
+
+static struct sk_buff *taprio_peek(struct Qdisc *sch)
+{
+	WARN_ONCE(1, "taprio only supports operating as root qdisc, peek() not implemented");
+	return NULL;
+}
 
-		if (numsegs > 1)
-			qdisc_tree_reduce_backlog(sch, 1 - numsegs, len - slen);
-		consume_skb(skb);
+static void taprio_set_budgets(struct taprio_sched *q,
+			       struct sched_gate_list *sched,
+			       struct sched_entry *entry)
+{
+	struct net_device *dev = qdisc_dev(q->root);
+	int num_tc = netdev_get_num_tc(dev);
+	int tc, budget;
 
-		return numsegs > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
+	for (tc = 0; tc < num_tc; tc++) {
+		/* Traffic classes which never close have infinite budget */
+		if (entry->gate_duration[tc] == sched->cycle_time)
+			budget = INT_MAX;
+		else
+			budget = div64_u64((u64)entry->gate_duration[tc] * PSEC_PER_NSEC,
+					   atomic64_read(&q->picos_per_byte));
+
+		atomic_set(&entry->budget[tc], budget);
 	}
+}
 
-	return taprio_enqueue_one(skb, sch, child, to_free);
+/* When an skb is sent, it consumes from the budget of all traffic classes */
+static int taprio_update_budgets(struct sched_entry *entry, size_t len,
+				 int tc_consumed, int num_tc)
+{
+	int tc, budget, new_budget = 0;
+
+	for (tc = 0; tc < num_tc; tc++) {
+		budget = atomic_read(&entry->budget[tc]);
+		/* Don't consume from infinite budget */
+		if (budget == INT_MAX) {
+			if (tc == tc_consumed)
+				new_budget = budget;
+			continue;
+		}
+
+		if (tc == tc_consumed)
+			new_budget = atomic_sub_return(len, &entry->budget[tc]);
+		else
+			atomic_sub(len, &entry->budget[tc]);
+	}
+
+	return new_budget;
 }
 
-/* Will not be called in the full offload case, since the TX queues are
- * attached to the Qdisc created using qdisc_create_dflt()
- */
-static struct sk_buff *taprio_peek(struct Qdisc *sch)
+static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
+					       struct sched_entry *entry,
+					       u32 gate_mask)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
-	struct sched_entry *entry;
+	struct Qdisc *child = q->qdiscs[txq];
+	int num_tc = netdev_get_num_tc(dev);
 	struct sk_buff *skb;
-	u32 gate_mask;
-	int i;
+	ktime_t guard;
+	int prio;
+	int len;
+	u8 tc;
 
-	rcu_read_lock();
-	entry = rcu_dereference(q->current_entry);
-	gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
-	rcu_read_unlock();
+	if (unlikely(!child))
+		return NULL;
 
-	if (!gate_mask)
+	if (TXTIME_ASSIST_IS_ENABLED(q->flags))
+		goto skip_peek_checks;
+
+	skb = child->ops->peek(child);
+	if (!skb)
 		return NULL;
 
-	for (i = 0; i < dev->num_tx_queues; i++) {
-		struct Qdisc *child = q->qdiscs[i];
-		int prio;
-		u8 tc;
+	prio = skb->priority;
+	tc = netdev_get_prio_tc_map(dev, prio);
 
-		if (unlikely(!child))
-			continue;
+	if (!(gate_mask & BIT(tc)))
+		return NULL;
 
-		skb = child->ops->peek(child);
-		if (!skb)
-			continue;
+	len = qdisc_pkt_len(skb);
+	guard = ktime_add_ns(taprio_get_time(q), length_to_duration(q, len));
 
-		if (TXTIME_ASSIST_IS_ENABLED(q->flags))
-			return skb;
+	/* In the case that there's no gate entry, there's no
+	 * guard band ...
+	 */
+	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
+	    !taprio_entry_allows_tx(guard, entry, tc))
+		return NULL;
+
+	/* ... and no budget. */
+	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
+	    taprio_update_budgets(entry, len, tc, num_tc) < 0)
+		return NULL;
+
+skip_peek_checks:
+	skb = child->ops->dequeue(child);
+	if (unlikely(!skb))
+		return NULL;
+
+	qdisc_bstats_update(sch, skb);
+	qdisc_qstats_backlog_dec(sch, skb);
+	sch->q.qlen--;
+
+	return skb;
+}
+
+static void taprio_next_tc_txq(struct net_device *dev, int tc, int *txq)
+{
+	int offset = dev->tc_to_txq[tc].offset;
+	int count = dev->tc_to_txq[tc].count;
+
+	(*txq)++;
+	if (*txq == offset + count)
+		*txq = offset;
+}
+
+/* Prioritize higher traffic classes, and select among TXQs belonging to the
+ * same TC using round robin
+ */
+static struct sk_buff *taprio_dequeue_tc_priority(struct Qdisc *sch,
+						  struct sched_entry *entry,
+						  u32 gate_mask)
+{
+	struct taprio_sched *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	int num_tc = netdev_get_num_tc(dev);
+	struct sk_buff *skb;
+	int tc;
 
-		prio = skb->priority;
-		tc = netdev_get_prio_tc_map(dev, prio);
+	for (tc = num_tc - 1; tc >= 0; tc--) {
+		int first_txq = q->cur_txq[tc];
 
 		if (!(gate_mask & BIT(tc)))
 			continue;
 
-		return skb;
+		do {
+			skb = taprio_dequeue_from_txq(sch, q->cur_txq[tc],
+						      entry, gate_mask);
+
+			taprio_next_tc_txq(dev, tc, &q->cur_txq[tc]);
+
+			if (skb)
+				return skb;
+		} while (q->cur_txq[tc] != first_txq);
 	}
 
 	return NULL;
 }
 
-static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
+/* Broken way of prioritizing smaller TXQ indices and ignoring the traffic
+ * class other than to determine whether the gate is open or not
+ */
+static struct sk_buff *taprio_dequeue_txq_priority(struct Qdisc *sch,
+						   struct sched_entry *entry,
+						   u32 gate_mask)
 {
-	atomic_set(&entry->budget,
-		   div64_u64((u64)entry->interval * PSEC_PER_NSEC,
-			     atomic64_read(&q->picos_per_byte)));
+	struct net_device *dev = qdisc_dev(sch);
+	struct sk_buff *skb;
+	int i;
+
+	for (i = 0; i < dev->num_tx_queues; i++) {
+		skb = taprio_dequeue_from_txq(sch, i, entry, gate_mask);
+		if (skb)
+			return skb;
+	}
+
+	return NULL;
 }
 
 /* Will not be called in the full offload case, since the TX queues are
@@ -559,11 +821,9 @@ static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
 static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
-	struct net_device *dev = qdisc_dev(sch);
 	struct sk_buff *skb = NULL;
 	struct sched_entry *entry;
 	u32 gate_mask;
-	int i;
 
 	rcu_read_lock();
 	entry = rcu_dereference(q->current_entry);
@@ -573,69 +833,23 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 	 * "AdminGateStates"
 	 */
 	gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
-
 	if (!gate_mask)
 		goto done;
 
-	for (i = 0; i < dev->num_tx_queues; i++) {
-		struct Qdisc *child = q->qdiscs[i];
-		ktime_t guard;
-		int prio;
-		int len;
-		u8 tc;
-
-		if (unlikely(!child))
-			continue;
-
-		if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
-			skb = child->ops->dequeue(child);
-			if (!skb)
-				continue;
-			goto skb_found;
-		}
-
-		skb = child->ops->peek(child);
-		if (!skb)
-			continue;
-
-		prio = skb->priority;
-		tc = netdev_get_prio_tc_map(dev, prio);
-
-		if (!(gate_mask & BIT(tc))) {
-			skb = NULL;
-			continue;
-		}
-
-		len = qdisc_pkt_len(skb);
-		guard = ktime_add_ns(taprio_get_time(q),
-				     length_to_duration(q, len));
-
-		/* In the case that there's no gate entry, there's no
-		 * guard band ...
-		 */
-		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
-		    ktime_after(guard, entry->close_time)) {
-			skb = NULL;
-			continue;
-		}
-
-		/* ... and no budget. */
-		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
-		    atomic_sub_return(len, &entry->budget) < 0) {
-			skb = NULL;
-			continue;
-		}
-
-		skb = child->ops->dequeue(child);
-		if (unlikely(!skb))
-			goto done;
-
-skb_found:
-		qdisc_bstats_update(sch, skb);
-		qdisc_qstats_backlog_dec(sch, skb);
-		sch->q.qlen--;
-
-		goto done;
+	if (static_branch_unlikely(&taprio_have_broken_mqprio) &&
+	    !static_branch_likely(&taprio_have_working_mqprio)) {
+		/* Single NIC kind which is broken */
+		skb = taprio_dequeue_txq_priority(sch, entry, gate_mask);
+	} else if (static_branch_likely(&taprio_have_working_mqprio) &&
+		   !static_branch_unlikely(&taprio_have_broken_mqprio)) {
+		/* Single NIC kind which prioritizes properly */
+		skb = taprio_dequeue_tc_priority(sch, entry, gate_mask);
+	} else {
+		/* Mixed NIC kinds present in system, need dynamic testing */
+		if (q->broken_mqprio)
+			skb = taprio_dequeue_txq_priority(sch, entry, gate_mask);
+		else
+			skb = taprio_dequeue_tc_priority(sch, entry, gate_mask);
 	}
 
 done:
@@ -650,7 +864,7 @@ static bool should_restart_cycle(const struct sched_gate_list *oper,
 	if (list_is_last(&entry->list, &oper->entries))
 		return true;
 
-	if (ktime_compare(entry->close_time, oper->cycle_close_time) == 0)
+	if (ktime_compare(entry->end_time, oper->cycle_end_time) == 0)
 		return true;
 
 	return false;
@@ -658,7 +872,7 @@ static bool should_restart_cycle(const struct sched_gate_list *oper,
 
 static bool should_change_schedules(const struct sched_gate_list *admin,
 				    const struct sched_gate_list *oper,
-				    ktime_t close_time)
+				    ktime_t end_time)
 {
 	ktime_t next_base_time, extension_time;
 
@@ -667,18 +881,18 @@ static bool should_change_schedules(const struct sched_gate_list *admin,
 
 	next_base_time = sched_base_time(admin);
 
-	/* This is the simple case, the close_time would fall after
+	/* This is the simple case, the end_time would fall after
 	 * the next schedule base_time.
 	 */
-	if (ktime_compare(next_base_time, close_time) <= 0)
+	if (ktime_compare(next_base_time, end_time) <= 0)
 		return true;
 
-	/* This is the cycle_time_extension case, if the close_time
+	/* This is the cycle_time_extension case, if the end_time
 	 * plus the amount that can be extended would fall after the
 	 * next schedule base_time, we can extend the current schedule
 	 * for that amount.
 	 */
-	extension_time = ktime_add_ns(close_time, oper->cycle_time_extension);
+	extension_time = ktime_add_ns(end_time, oper->cycle_time_extension);
 
 	/* FIXME: the IEEE 802.1Q-2018 Specification isn't clear about
 	 * how precisely the extension should be made. So after
@@ -694,10 +908,13 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 {
 	struct taprio_sched *q = container_of(timer, struct taprio_sched,
 					      advance_timer);
+	struct net_device *dev = qdisc_dev(q->root);
 	struct sched_gate_list *oper, *admin;
+	int num_tc = netdev_get_num_tc(dev);
 	struct sched_entry *entry, *next;
 	struct Qdisc *sch = q->root;
-	ktime_t close_time;
+	ktime_t end_time;
+	int tc;
 
 	spin_lock(&q->current_entry_lock);
 	entry = rcu_dereference_protected(q->current_entry,
@@ -716,41 +933,49 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 	 * entry of all schedules are pre-calculated during the
 	 * schedule initialization.
 	 */
-	if (unlikely(!entry || entry->close_time == oper->base_time)) {
+	if (unlikely(!entry || entry->end_time == oper->base_time)) {
 		next = list_first_entry(&oper->entries, struct sched_entry,
 					list);
-		close_time = next->close_time;
+		end_time = next->end_time;
 		goto first_run;
 	}
 
 	if (should_restart_cycle(oper, entry)) {
 		next = list_first_entry(&oper->entries, struct sched_entry,
 					list);
-		oper->cycle_close_time = ktime_add_ns(oper->cycle_close_time,
-						      oper->cycle_time);
+		oper->cycle_end_time = ktime_add_ns(oper->cycle_end_time,
+						    oper->cycle_time);
 	} else {
 		next = list_next_entry(entry, list);
 	}
 
-	close_time = ktime_add_ns(entry->close_time, next->interval);
-	close_time = min_t(ktime_t, close_time, oper->cycle_close_time);
+	end_time = ktime_add_ns(entry->end_time, next->interval);
+	end_time = min_t(ktime_t, end_time, oper->cycle_end_time);
+
+	for (tc = 0; tc < num_tc; tc++) {
+		if (next->gate_duration[tc] == oper->cycle_time)
+			next->gate_close_time[tc] = KTIME_MAX;
+		else
+			next->gate_close_time[tc] = ktime_add_ns(entry->end_time,
+								 next->gate_duration[tc]);
+	}
 
-	if (should_change_schedules(admin, oper, close_time)) {
+	if (should_change_schedules(admin, oper, end_time)) {
 		/* Set things so the next time this runs, the new
 		 * schedule runs.
 		 */
-		close_time = sched_base_time(admin);
+		end_time = sched_base_time(admin);
 		switch_schedules(q, &admin, &oper);
 	}
 
-	next->close_time = close_time;
-	taprio_set_budget(q, next);
+	next->end_time = end_time;
+	taprio_set_budgets(q, oper, next);
 
 first_run:
 	rcu_assign_pointer(q->current_entry, next);
 	spin_unlock(&q->current_entry_lock);
 
-	hrtimer_set_expires(&q->advance_timer, close_time);
+	hrtimer_set_expires(&q->advance_timer, end_time);
 
 	rcu_read_lock();
 	__netif_schedule(sch);
@@ -918,6 +1143,8 @@ static int parse_taprio_schedule(struct taprio_sched *q, struct nlattr **tb,
 		new->cycle_time = cycle;
 	}
 
+	taprio_calculate_gate_durations(q, new);
+
 	return 0;
 }
 
@@ -986,11 +1213,14 @@ static int taprio_get_start_time(struct Qdisc *sch,
 	return 0;
 }
 
-static void setup_first_close_time(struct taprio_sched *q,
-				   struct sched_gate_list *sched, ktime_t base)
+static void setup_first_end_time(struct taprio_sched *q,
+				 struct sched_gate_list *sched, ktime_t base)
 {
+	struct net_device *dev = qdisc_dev(q->root);
+	int num_tc = netdev_get_num_tc(dev);
 	struct sched_entry *first;
 	ktime_t cycle;
+	int tc;
 
 	first = list_first_entry(&sched->entries,
 				 struct sched_entry, list);
@@ -998,10 +1228,18 @@ static void setup_first_close_time(struct taprio_sched *q,
 	cycle = sched->cycle_time;
 
 	/* FIXME: find a better place to do this */
-	sched->cycle_close_time = ktime_add_ns(base, cycle);
+	sched->cycle_end_time = ktime_add_ns(base, cycle);
+
+	first->end_time = ktime_add_ns(base, first->interval);
+	taprio_set_budgets(q, sched, first);
+
+	for (tc = 0; tc < num_tc; tc++) {
+		if (first->gate_duration[tc] == sched->cycle_time)
+			first->gate_close_time[tc] = KTIME_MAX;
+		else
+			first->gate_close_time[tc] = ktime_add_ns(base, first->gate_duration[tc]);
+	}
 
-	first->close_time = ktime_add_ns(base, first->interval);
-	taprio_set_budget(q, first);
 	rcu_assign_pointer(q->current_entry, NULL);
 }
 
@@ -1055,6 +1293,8 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
 			       void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct sched_gate_list *oper, *admin;
+	struct qdisc_size_table *stab;
 	struct taprio_sched *q;
 
 	ASSERT_RTNL();
@@ -1067,6 +1307,17 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
 			continue;
 
 		taprio_set_picos_per_byte(dev, q);
+
+		stab = rtnl_dereference(q->root->stab);
+
+		oper = rtnl_dereference(q->oper_sched);
+		if (oper)
+			taprio_update_queue_max_sdu(q, oper, stab);
+
+		admin = rtnl_dereference(q->admin_sched);
+		if (admin)
+			taprio_update_queue_max_sdu(q, admin, stab);
+
 		break;
 	}
 
@@ -1197,6 +1448,34 @@ static void taprio_sched_to_offload(struct net_device *dev,
 	offload->num_entries = i;
 }
 
+static void taprio_detect_broken_mqprio(struct taprio_sched *q)
+{
+	struct net_device *dev = qdisc_dev(q->root);
+	struct tc_taprio_caps caps;
+
+	qdisc_offload_query_caps(dev, TC_SETUP_QDISC_TAPRIO,
+				 &caps, sizeof(caps));
+
+	q->broken_mqprio = caps.broken_mqprio;
+	if (q->broken_mqprio)
+		static_branch_inc(&taprio_have_broken_mqprio);
+	else
+		static_branch_inc(&taprio_have_working_mqprio);
+
+	q->detected_mqprio = true;
+}
+
+static void taprio_cleanup_broken_mqprio(struct taprio_sched *q)
+{
+	if (!q->detected_mqprio)
+		return;
+
+	if (q->broken_mqprio)
+		static_branch_dec(&taprio_have_broken_mqprio);
+	else
+		static_branch_dec(&taprio_have_working_mqprio);
+}
+
 static int taprio_enable_offload(struct net_device *dev,
 				 struct taprio_sched *q,
 				 struct sched_gate_list *sched,
@@ -1425,7 +1704,6 @@ static int taprio_parse_tc_entries(struct Qdisc *sch,
 				   struct netlink_ext_ack *extack)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
-	struct net_device *dev = qdisc_dev(sch);
 	u32 max_sdu[TC_QOPT_MAX_QUEUE];
 	unsigned long seen_tcs = 0;
 	struct nlattr *n;
@@ -1439,18 +1717,14 @@ static int taprio_parse_tc_entries(struct Qdisc *sch,
 		if (nla_type(n) != TCA_TAPRIO_ATTR_TC_ENTRY)
 			continue;
 
-		err = taprio_parse_tc_entry(sch, n, max_sdu, &seen_tcs, extack);
+		err = taprio_parse_tc_entry(sch, n, max_sdu, &seen_tcs,
+					    extack);
 		if (err)
 			goto out;
 	}
 
-	for (tc = 0; tc < TC_QOPT_MAX_QUEUE; tc++) {
+	for (tc = 0; tc < TC_QOPT_MAX_QUEUE; tc++)
 		q->max_sdu[tc] = max_sdu[tc];
-		if (max_sdu[tc])
-			q->max_frm_len[tc] = max_sdu[tc] + dev->hard_header_len;
-		else
-			q->max_frm_len[tc] = U32_MAX; /* never oversized */
-	}
 
 out:
 	return err;
@@ -1506,6 +1780,7 @@ static int taprio_new_flags(const struct nlattr *attr, u32 old,
 static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 			 struct netlink_ext_ack *extack)
 {
+	struct qdisc_size_table *stab = rtnl_dereference(sch->stab);
 	struct nlattr *tb[TCA_TAPRIO_ATTR_MAX + 1] = { };
 	struct sched_gate_list *oper, *admin, *new_admin;
 	struct taprio_sched *q = qdisc_priv(sch);
@@ -1573,15 +1848,18 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 		goto free_sched;
 
 	taprio_set_picos_per_byte(dev, q);
+	taprio_update_queue_max_sdu(q, new_admin, stab);
 
 	if (mqprio) {
 		err = netdev_set_num_tc(dev, mqprio->num_tc);
 		if (err)
 			goto free_sched;
-		for (i = 0; i < mqprio->num_tc; i++)
+		for (i = 0; i < mqprio->num_tc; i++) {
 			netdev_set_tc_queue(dev, i,
 					    mqprio->count[i],
 					    mqprio->offset[i]);
+			q->cur_txq[i] = mqprio->offset[i];
+		}
 
 		/* Always use supplied priority mappings */
 		for (i = 0; i <= TC_BITMASK; i++)
@@ -1636,7 +1914,7 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 		if (admin)
 			call_rcu(&admin->rcu, taprio_free_sched_cb);
 	} else {
-		setup_first_close_time(q, new_admin, start);
+		setup_first_end_time(q, new_admin, start);
 
 		/* Protects against advance_sched() */
 		spin_lock_irqsave(&q->current_entry_lock, flags);
@@ -1656,6 +1934,10 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	new_admin = NULL;
 	err = 0;
 
+	if (!stab)
+		NL_SET_ERR_MSG_MOD(extack,
+				   "Size table not specified, frame length estimations may be inaccurate");
+
 unlock:
 	spin_unlock_bh(qdisc_lock(sch));
 
@@ -1716,6 +1998,8 @@ static void taprio_destroy(struct Qdisc *sch)
 
 	if (admin)
 		call_rcu(&admin->rcu, taprio_free_sched_cb);
+
+	taprio_cleanup_broken_mqprio(q);
 }
 
 static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
@@ -1780,6 +2064,8 @@ static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
 		q->qdiscs[i] = qdisc;
 	}
 
+	taprio_detect_broken_mqprio(q);
+
 	return taprio_change(sch, opt, extack);
 }
 
@@ -1920,7 +2206,8 @@ static int dump_schedule(struct sk_buff *msg,
 	return -1;
 }
 
-static int taprio_dump_tc_entries(struct taprio_sched *q, struct sk_buff *skb)
+static int taprio_dump_tc_entries(struct sk_buff *skb,
+				  struct sched_gate_list *sched)
 {
 	struct nlattr *n;
 	int tc;
@@ -1934,7 +2221,7 @@ static int taprio_dump_tc_entries(struct taprio_sched *q, struct sk_buff *skb)
 			goto nla_put_failure;
 
 		if (nla_put_u32(skb, TCA_TAPRIO_TC_ENTRY_MAX_SDU,
-				q->max_sdu[tc]))
+				sched->max_sdu[tc]))
 			goto nla_put_failure;
 
 		nla_nest_end(skb, n);
@@ -1978,7 +2265,7 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 	    nla_put_u32(skb, TCA_TAPRIO_ATTR_TXTIME_DELAY, q->txtime_delay))
 		goto options_error;
 
-	if (taprio_dump_tc_entries(q, skb))
+	if (oper && taprio_dump_tc_entries(skb, oper))
 		goto options_error;
 
 	if (oper && dump_schedule(skb, oper))