net-sysfs: Add interface for Rx queue(s) map per Tx queue

Extend transmit queue sysfs attribute to configure Rx queue(s) map
per Tx queue. By default no receive queues are configured for the
Tx queue.

- /sys/class/net/eth0/queues/tx-*/xps_rxqs
Signed-off-by: NAmritha Nambiar <amritha.nambiar@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/net-sysfs.c

@@ -1283,6 +1283,88 @@ static ssize_t xps_cpus_store(struct netdev_queue *queue,
 
 static struct netdev_queue_attribute xps_cpus_attribute __ro_after_init
 	= __ATTR_RW(xps_cpus);
+
+static ssize_t xps_rxqs_show(struct netdev_queue *queue, char *buf)
+{
+	struct net_device *dev = queue->dev;
+	struct xps_dev_maps *dev_maps;
+	unsigned long *mask, index;
+	int j, len, num_tc = 1, tc = 0;
+
+	index = get_netdev_queue_index(queue);
+
+	if (dev->num_tc) {
+		num_tc = dev->num_tc;
+		tc = netdev_txq_to_tc(dev, index);
+		if (tc < 0)
+			return -EINVAL;
+	}
+	mask = kcalloc(BITS_TO_LONGS(dev->num_rx_queues), sizeof(long),
+		       GFP_KERNEL);
+	if (!mask)
+		return -ENOMEM;
+
+	rcu_read_lock();
+	dev_maps = rcu_dereference(dev->xps_rxqs_map);
+	if (!dev_maps)
+		goto out_no_maps;
+
+	for (j = -1; j = netif_attrmask_next(j, NULL, dev->num_rx_queues),
+	     j < dev->num_rx_queues;) {
+		int i, tci = j * num_tc + tc;
+		struct xps_map *map;
+
+		map = rcu_dereference(dev_maps->attr_map[tci]);
+		if (!map)
+			continue;
+
+		for (i = map->len; i--;) {
+			if (map->queues[i] == index) {
+				set_bit(j, mask);
+				break;
+			}
+		}
+	}
+out_no_maps:
+	rcu_read_unlock();
+
+	len = bitmap_print_to_pagebuf(false, buf, mask, dev->num_rx_queues);
+	kfree(mask);
+
+	return len < PAGE_SIZE ? len : -EINVAL;
+}
+
+static ssize_t xps_rxqs_store(struct netdev_queue *queue, const char *buf,
+			      size_t len)
+{
+	struct net_device *dev = queue->dev;
+	struct net *net = dev_net(dev);
+	unsigned long *mask, index;
+	int err;
+
+	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+		return -EPERM;
+
+	mask = kcalloc(BITS_TO_LONGS(dev->num_rx_queues), sizeof(long),
+		       GFP_KERNEL);
+	if (!mask)
+		return -ENOMEM;
+
+	index = get_netdev_queue_index(queue);
+
+	err = bitmap_parse(buf, len, mask, dev->num_rx_queues);
+	if (err) {
+		kfree(mask);
+		return err;
+	}
+
+	err = __netif_set_xps_queue(dev, mask, index, true);
+	kfree(mask);
+	return err ? : len;
+}
+
+static struct netdev_queue_attribute xps_rxqs_attribute __ro_after_init
+	= __ATTR_RW(xps_rxqs);
 #endif /* CONFIG_XPS */
 
 static struct attribute *netdev_queue_default_attrs[] __ro_after_init = {
@@ -1290,6 +1372,7 @@ static struct attribute *netdev_queue_default_attrs[] __ro_after_init = {
 	&queue_traffic_class.attr,
 #ifdef CONFIG_XPS
 	&xps_cpus_attribute.attr,
+	&xps_rxqs_attribute.attr,
 	&queue_tx_maxrate.attr,
 #endif
 	NULL