mqprio: Change handling of hw u8 to allow for multiple hardware offload modes

This patch is meant to allow for support of multiple hardware offload type
for a single device. There is currently no bounds checking for the hw
member of the mqprio_qopt structure.  This results in us being able to pass
values from 1 to 255 with all being treated the same.  On retreiving the
value it is returned as 1 for anything 1 or greater being set.

With this change we are currently adding limited bounds checking by
defining an enum and using those values to limit the reported hardware
offloads.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/pkt_sched.h

@@ -617,6 +617,14 @@ struct tc_drr_stats {
 #define TC_QOPT_BITMASK 15
 #define TC_QOPT_MAX_QUEUE 16
 
+enum {
+	TC_MQPRIO_HW_OFFLOAD_NONE,	/* no offload requested */
+	TC_MQPRIO_HW_OFFLOAD_TCS,	/* offload TCs, no queue counts */
+	__TC_MQPRIO_HW_OFFLOAD_MAX
+};
+
+#define TC_MQPRIO_HW_OFFLOAD_MAX (__TC_MQPRIO_HW_OFFLOAD_MAX - 1)
+
 struct tc_mqprio_qopt {
 	__u8	num_tc;
 	__u8	prio_tc_map[TC_QOPT_BITMASK + 1];

net/sched/sch_mqprio.c

@@ -21,7 +21,7 @@
 
 struct mqprio_sched {
 	struct Qdisc		**qdiscs;
-	int hw_owned;
+	int hw_offload;
 };
 
 static void mqprio_destroy(struct Qdisc *sch)
@@ -39,7 +39,7 @@ static void mqprio_destroy(struct Qdisc *sch)
 		kfree(priv->qdiscs);
 	}
 
-	if (priv->hw_owned && dev->netdev_ops->ndo_setup_tc)
+	if (priv->hw_offload && dev->netdev_ops->ndo_setup_tc)
 		dev->netdev_ops->ndo_setup_tc(dev, sch->handle, 0, &tc);
 	else
 		netdev_set_num_tc(dev, 0);
@@ -59,15 +59,20 @@ static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
 			return -EINVAL;
 	}
 
-	/* net_device does not support requested operation */
-	if (qopt->hw && !dev->netdev_ops->ndo_setup_tc)
-		return -EINVAL;
+	/* Limit qopt->hw to maximum supported offload value.  Drivers have
+	 * the option of overriding this later if they don't support the a
+	 * given offload type.
+	 */
+	if (qopt->hw > TC_MQPRIO_HW_OFFLOAD_MAX)
+		qopt->hw = TC_MQPRIO_HW_OFFLOAD_MAX;
 
-	/* if hw owned qcount and qoffset are taken from LLD so
-	 * no reason to verify them here
+	/* 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 (qopt->hw)
-		return 0;
+		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];
@@ -142,10 +147,11 @@ static int mqprio_init(struct Qdisc *sch, struct nlattr *opt)
 		struct tc_to_netdev tc = {.type = TC_SETUP_MQPRIO,
 					  { .tc = qopt->num_tc }};
 
-		priv->hw_owned = 1;
 		err = dev->netdev_ops->ndo_setup_tc(dev, sch->handle, 0, &tc);
 		if (err)
 			return err;
+
+		priv->hw_offload = qopt->hw;
 	} else {
 		netdev_set_num_tc(dev, qopt->num_tc);
 		for (i = 0; i < qopt->num_tc; i++)
@@ -243,7 +249,7 @@ static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 
 	opt.num_tc = netdev_get_num_tc(dev);
 	memcpy(opt.prio_tc_map, dev->prio_tc_map, sizeof(opt.prio_tc_map));
-	opt.hw = priv->hw_owned;
+	opt.hw = priv->hw_offload;
 
 	for (i = 0; i < netdev_get_num_tc(dev); i++) {
 		opt.count[i] = dev->tc_to_txq[i].count;