Merge branch 'netdevsim-support-for-l3-hw-stats'

Petr Machata says:

====================
netdevsim: Support for L3 HW stats

"L3 stats" is a suite of interface statistics aimed at reflecting traffic
taking place in a HW device, on an object corresponding to some software
netdevice. Support for this stats suite has been added recently, in commit
ca0a53dc ("Merge branch 'net-hw-counters-for-soft-devices'").

In this patch set:

- Patch #1 adds support for L3 stats to netdevsim.

  Real devices can have various conditions for when an L3 counter is
  available. To simulate this, netdevsim maintains a list of devices
  suitable for HW stats collection. Only when l3_stats is enabled on both a
  netdevice itself, and in netdevsim, will netdevsim contribute values to
  L3 stats.

  This enablement and disablement is done via debugfs:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/enable_ifindex
    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/disable_ifindex

  Besides this, there is a third toggle to mark a device for future failure:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/fail_next_enable

- This allows HW-independent testing of stats reporting and in-kernel APIs,
  as well as a test for enablement rollback, which is difficult to do
  otherwise. This netdevsim-specific selftest is added in patch #2.

- Patch #3 adds another driver-specific selftest, namely a test aimed at
  checking mlxsw-induced stats monitoring events.

====================

Link: https://lore.kernel.org/r/cover.1647265833.git.petrm@nvidia.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/netdevsim/Makefile

@@ -3,7 +3,7 @@
 obj-$(CONFIG_NETDEVSIM) += netdevsim.o
 
 netdevsim-objs := \
-	netdev.o dev.o ethtool.o fib.o bus.o health.o udp_tunnels.o
+	netdev.o dev.o ethtool.o fib.o bus.o health.o hwstats.o udp_tunnels.o
 
 ifeq ($(CONFIG_BPF_SYSCALL),y)
 netdevsim-objs += \

drivers/net/netdevsim/dev.c

@@ -1498,10 +1498,14 @@ static int nsim_dev_reload_create(struct nsim_dev *nsim_dev,
 	if (err)
 		goto err_health_exit;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_hwstats_init(nsim_dev);
 	if (err)
 		goto err_psample_exit;
 
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_hwstats_exit;
+
 	nsim_dev->take_snapshot = debugfs_create_file("take_snapshot",
 						      0200,
 						      nsim_dev->ddir,
@@ -1509,6 +1513,8 @@ static int nsim_dev_reload_create(struct nsim_dev *nsim_dev,
 						&nsim_dev_take_snapshot_fops);
 	return 0;
 
+err_hwstats_exit:
+	nsim_dev_hwstats_exit(nsim_dev);
 err_psample_exit:
 	nsim_dev_psample_exit(nsim_dev);
 err_health_exit:
@@ -1595,15 +1601,21 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
 	if (err)
 		goto err_bpf_dev_exit;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_hwstats_init(nsim_dev);
 	if (err)
 		goto err_psample_exit;
 
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_hwstats_exit;
+
 	nsim_dev->esw_mode = DEVLINK_ESWITCH_MODE_LEGACY;
 	devlink_set_features(devlink, DEVLINK_F_RELOAD);
 	devlink_register(devlink);
 	return 0;
 
+err_hwstats_exit:
+	nsim_dev_hwstats_exit(nsim_dev);
 err_psample_exit:
 	nsim_dev_psample_exit(nsim_dev);
 err_bpf_dev_exit:
@@ -1648,6 +1660,7 @@ static void nsim_dev_reload_destroy(struct nsim_dev *nsim_dev)
 	mutex_unlock(&nsim_dev->vfs_lock);
 
 	nsim_dev_port_del_all(nsim_dev);
+	nsim_dev_hwstats_exit(nsim_dev);
 	nsim_dev_psample_exit(nsim_dev);
 	nsim_dev_health_exit(nsim_dev);
 	nsim_fib_destroy(devlink, nsim_dev->fib_data);

drivers/net/netdevsim/hwstats.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/debugfs.h>
+
+#include "netdevsim.h"
+
+#define NSIM_DEV_HWSTATS_TRAFFIC_MS	100
+
+static struct list_head *
+nsim_dev_hwstats_get_list_head(struct nsim_dev_hwstats *hwstats,
+			       enum netdev_offload_xstats_type type)
+{
+	switch (type) {
+	case NETDEV_OFFLOAD_XSTATS_TYPE_L3:
+		return &hwstats->l3_list;
+	}
+
+	WARN_ON_ONCE(1);
+	return NULL;
+}
+
+static void nsim_dev_hwstats_traffic_bump(struct nsim_dev_hwstats *hwstats,
+					  enum netdev_offload_xstats_type type)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	struct list_head *hwsdev_list;
+
+	hwsdev_list = nsim_dev_hwstats_get_list_head(hwstats, type);
+	if (WARN_ON(!hwsdev_list))
+		return;
+
+	list_for_each_entry(hwsdev, hwsdev_list, list) {
+		if (hwsdev->enabled) {
+			hwsdev->stats.rx_packets += 1;
+			hwsdev->stats.tx_packets += 2;
+			hwsdev->stats.rx_bytes += 100;
+			hwsdev->stats.tx_bytes += 300;
+		}
+	}
+}
+
+static void nsim_dev_hwstats_traffic_work(struct work_struct *work)
+{
+	struct nsim_dev_hwstats *hwstats;
+
+	hwstats = container_of(work, struct nsim_dev_hwstats, traffic_dw.work);
+	mutex_lock(&hwstats->hwsdev_list_lock);
+	nsim_dev_hwstats_traffic_bump(hwstats, NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+
+	schedule_delayed_work(&hwstats->traffic_dw,
+			      msecs_to_jiffies(NSIM_DEV_HWSTATS_TRAFFIC_MS));
+}
+
+static struct nsim_dev_hwstats_netdev *
+nsim_dev_hwslist_find_hwsdev(struct list_head *hwsdev_list,
+			     int ifindex)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+
+	list_for_each_entry(hwsdev, hwsdev_list, list) {
+		if (hwsdev->netdev->ifindex == ifindex)
+			return hwsdev;
+	}
+
+	return NULL;
+}
+
+static int nsim_dev_hwsdev_enable(struct nsim_dev_hwstats_netdev *hwsdev,
+				  struct netlink_ext_ack *extack)
+{
+	if (hwsdev->fail_enable) {
+		hwsdev->fail_enable = false;
+		NL_SET_ERR_MSG_MOD(extack, "Stats enablement set to fail");
+		return -ECANCELED;
+	}
+
+	hwsdev->enabled = true;
+	return 0;
+}
+
+static void nsim_dev_hwsdev_disable(struct nsim_dev_hwstats_netdev *hwsdev)
+{
+	hwsdev->enabled = false;
+	memset(&hwsdev->stats, 0, sizeof(hwsdev->stats));
+}
+
+static int
+nsim_dev_hwsdev_report_delta(struct nsim_dev_hwstats_netdev *hwsdev,
+			     struct netdev_notifier_offload_xstats_info *info)
+{
+	netdev_offload_xstats_report_delta(info->report_delta, &hwsdev->stats);
+	memset(&hwsdev->stats, 0, sizeof(hwsdev->stats));
+	return 0;
+}
+
+static void
+nsim_dev_hwsdev_report_used(struct nsim_dev_hwstats_netdev *hwsdev,
+			    struct netdev_notifier_offload_xstats_info *info)
+{
+	if (hwsdev->enabled)
+		netdev_offload_xstats_report_used(info->report_used);
+}
+
+static int nsim_dev_hwstats_event_off_xstats(struct nsim_dev_hwstats *hwstats,
+					     struct net_device *dev,
+					     unsigned long event, void *ptr)
+{
+	struct netdev_notifier_offload_xstats_info *info;
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	struct list_head *hwsdev_list;
+	int err = 0;
+
+	info = ptr;
+	hwsdev_list = nsim_dev_hwstats_get_list_head(hwstats, info->type);
+	if (!hwsdev_list)
+		return 0;
+
+	mutex_lock(&hwstats->hwsdev_list_lock);
+
+	hwsdev = nsim_dev_hwslist_find_hwsdev(hwsdev_list, dev->ifindex);
+	if (!hwsdev)
+		goto out;
+
+	switch (event) {
+	case NETDEV_OFFLOAD_XSTATS_ENABLE:
+		err = nsim_dev_hwsdev_enable(hwsdev, info->info.extack);
+		break;
+	case NETDEV_OFFLOAD_XSTATS_DISABLE:
+		nsim_dev_hwsdev_disable(hwsdev);
+		break;
+	case NETDEV_OFFLOAD_XSTATS_REPORT_USED:
+		nsim_dev_hwsdev_report_used(hwsdev, info);
+		break;
+	case NETDEV_OFFLOAD_XSTATS_REPORT_DELTA:
+		err = nsim_dev_hwsdev_report_delta(hwsdev, info);
+		break;
+	}
+
+out:
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+	return err;
+}
+
+static void nsim_dev_hwsdev_fini(struct nsim_dev_hwstats_netdev *hwsdev)
+{
+	dev_put(hwsdev->netdev);
+	kfree(hwsdev);
+}
+
+static void
+__nsim_dev_hwstats_event_unregister(struct nsim_dev_hwstats *hwstats,
+				    struct net_device *dev,
+				    enum netdev_offload_xstats_type type)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	struct list_head *hwsdev_list;
+
+	hwsdev_list = nsim_dev_hwstats_get_list_head(hwstats, type);
+	if (WARN_ON(!hwsdev_list))
+		return;
+
+	hwsdev = nsim_dev_hwslist_find_hwsdev(hwsdev_list, dev->ifindex);
+	if (!hwsdev)
+		return;
+
+	list_del(&hwsdev->list);
+	nsim_dev_hwsdev_fini(hwsdev);
+}
+
+static void nsim_dev_hwstats_event_unregister(struct nsim_dev_hwstats *hwstats,
+					      struct net_device *dev)
+{
+	mutex_lock(&hwstats->hwsdev_list_lock);
+	__nsim_dev_hwstats_event_unregister(hwstats, dev,
+					    NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+}
+
+static int nsim_dev_hwstats_event(struct nsim_dev_hwstats *hwstats,
+				  struct net_device *dev,
+				  unsigned long event, void *ptr)
+{
+	switch (event) {
+	case NETDEV_OFFLOAD_XSTATS_ENABLE:
+	case NETDEV_OFFLOAD_XSTATS_DISABLE:
+	case NETDEV_OFFLOAD_XSTATS_REPORT_USED:
+	case NETDEV_OFFLOAD_XSTATS_REPORT_DELTA:
+		return nsim_dev_hwstats_event_off_xstats(hwstats, dev,
+							 event, ptr);
+	case NETDEV_UNREGISTER:
+		nsim_dev_hwstats_event_unregister(hwstats, dev);
+		break;
+	}
+
+	return 0;
+}
+
+static int nsim_dev_netdevice_event(struct notifier_block *nb,
+				    unsigned long event, void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct nsim_dev_hwstats *hwstats;
+	int err = 0;
+
+	hwstats = container_of(nb, struct nsim_dev_hwstats, netdevice_nb);
+	err = nsim_dev_hwstats_event(hwstats, dev, event, ptr);
+	if (err)
+		return notifier_from_errno(err);
+
+	return NOTIFY_OK;
+}
+
+static int
+nsim_dev_hwstats_enable_ifindex(struct nsim_dev_hwstats *hwstats,
+				int ifindex,
+				enum netdev_offload_xstats_type type,
+				struct list_head *hwsdev_list)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	struct nsim_dev *nsim_dev;
+	struct net_device *netdev;
+	bool notify = false;
+	struct net *net;
+	int err = 0;
+
+	nsim_dev = container_of(hwstats, struct nsim_dev, hwstats);
+	net = nsim_dev_net(nsim_dev);
+
+	rtnl_lock();
+	mutex_lock(&hwstats->hwsdev_list_lock);
+	hwsdev = nsim_dev_hwslist_find_hwsdev(hwsdev_list, ifindex);
+	if (hwsdev)
+		goto out_unlock_list;
+
+	netdev = dev_get_by_index(net, ifindex);
+	if (!netdev) {
+		err = -ENODEV;
+		goto out_unlock_list;
+	}
+
+	hwsdev = kzalloc(sizeof(*hwsdev), GFP_KERNEL);
+	if (!hwsdev) {
+		err = -ENOMEM;
+		goto out_put_netdev;
+	}
+
+	hwsdev->netdev = netdev;
+	list_add_tail(&hwsdev->list, hwsdev_list);
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+
+	if (netdev_offload_xstats_enabled(netdev, type)) {
+		nsim_dev_hwsdev_enable(hwsdev, NULL);
+		notify = true;
+	}
+
+	if (notify)
+		rtnl_offload_xstats_notify(netdev);
+	rtnl_unlock();
+	return err;
+
+out_put_netdev:
+	dev_put(netdev);
+out_unlock_list:
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+	rtnl_unlock();
+	return err;
+}
+
+static int
+nsim_dev_hwstats_disable_ifindex(struct nsim_dev_hwstats *hwstats,
+				 int ifindex,
+				 enum netdev_offload_xstats_type type,
+				 struct list_head *hwsdev_list)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	int err = 0;
+
+	rtnl_lock();
+	mutex_lock(&hwstats->hwsdev_list_lock);
+	hwsdev = nsim_dev_hwslist_find_hwsdev(hwsdev_list, ifindex);
+	if (hwsdev)
+		list_del(&hwsdev->list);
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+
+	if (!hwsdev) {
+		err = -ENOENT;
+		goto unlock_out;
+	}
+
+	if (netdev_offload_xstats_enabled(hwsdev->netdev, type)) {
+		netdev_offload_xstats_push_delta(hwsdev->netdev, type,
+						 &hwsdev->stats);
+		rtnl_offload_xstats_notify(hwsdev->netdev);
+	}
+	nsim_dev_hwsdev_fini(hwsdev);
+
+unlock_out:
+	rtnl_unlock();
+	return err;
+}
+
+static int
+nsim_dev_hwstats_fail_ifindex(struct nsim_dev_hwstats *hwstats,
+			      int ifindex,
+			      enum netdev_offload_xstats_type type,
+			      struct list_head *hwsdev_list)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev;
+	int err = 0;
+
+	mutex_lock(&hwstats->hwsdev_list_lock);
+
+	hwsdev = nsim_dev_hwslist_find_hwsdev(hwsdev_list, ifindex);
+	if (!hwsdev) {
+		err = -ENOENT;
+		goto err_hwsdev_list_unlock;
+	}
+
+	hwsdev->fail_enable = true;
+
+err_hwsdev_list_unlock:
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+	return err;
+}
+
+enum nsim_dev_hwstats_do {
+	NSIM_DEV_HWSTATS_DO_DISABLE,
+	NSIM_DEV_HWSTATS_DO_ENABLE,
+	NSIM_DEV_HWSTATS_DO_FAIL,
+};
+
+struct nsim_dev_hwstats_fops {
+	const struct file_operations fops;
+	enum nsim_dev_hwstats_do action;
+	enum netdev_offload_xstats_type type;
+};
+
+static ssize_t
+nsim_dev_hwstats_do_write(struct file *file,
+			  const char __user *data,
+			  size_t count, loff_t *ppos)
+{
+	struct nsim_dev_hwstats *hwstats = file->private_data;
+	struct nsim_dev_hwstats_fops *hwsfops;
+	struct list_head *hwsdev_list;
+	int ifindex;
+	int err;
+
+	hwsfops = container_of(debugfs_real_fops(file),
+			       struct nsim_dev_hwstats_fops, fops);
+
+	err = kstrtoint_from_user(data, count, 0, &ifindex);
+	if (err)
+		return err;
+
+	hwsdev_list = nsim_dev_hwstats_get_list_head(hwstats, hwsfops->type);
+	if (WARN_ON(!hwsdev_list))
+		return -EINVAL;
+
+	switch (hwsfops->action) {
+	case NSIM_DEV_HWSTATS_DO_DISABLE:
+		err = nsim_dev_hwstats_disable_ifindex(hwstats, ifindex,
+						       hwsfops->type,
+						       hwsdev_list);
+		break;
+	case NSIM_DEV_HWSTATS_DO_ENABLE:
+		err = nsim_dev_hwstats_enable_ifindex(hwstats, ifindex,
+						      hwsfops->type,
+						      hwsdev_list);
+		break;
+	case NSIM_DEV_HWSTATS_DO_FAIL:
+		err = nsim_dev_hwstats_fail_ifindex(hwstats, ifindex,
+						    hwsfops->type,
+						    hwsdev_list);
+		break;
+	}
+	if (err)
+		return err;
+
+	return count;
+}
+
+#define NSIM_DEV_HWSTATS_FOPS(ACTION, TYPE)			\
+	{							\
+		.fops = {					\
+			.open = simple_open,			\
+			.write = nsim_dev_hwstats_do_write,	\
+			.llseek = generic_file_llseek,		\
+			.owner = THIS_MODULE,			\
+		},						\
+		.action = ACTION,				\
+		.type = TYPE,					\
+	}
+
+static const struct nsim_dev_hwstats_fops nsim_dev_hwstats_l3_disable_fops =
+	NSIM_DEV_HWSTATS_FOPS(NSIM_DEV_HWSTATS_DO_DISABLE,
+			      NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+
+static const struct nsim_dev_hwstats_fops nsim_dev_hwstats_l3_enable_fops =
+	NSIM_DEV_HWSTATS_FOPS(NSIM_DEV_HWSTATS_DO_ENABLE,
+			      NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+
+static const struct nsim_dev_hwstats_fops nsim_dev_hwstats_l3_fail_fops =
+	NSIM_DEV_HWSTATS_FOPS(NSIM_DEV_HWSTATS_DO_FAIL,
+			      NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+
+#undef NSIM_DEV_HWSTATS_FOPS
+
+int nsim_dev_hwstats_init(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_hwstats *hwstats = &nsim_dev->hwstats;
+	struct net *net = nsim_dev_net(nsim_dev);
+	int err;
+
+	mutex_init(&hwstats->hwsdev_list_lock);
+	INIT_LIST_HEAD(&hwstats->l3_list);
+
+	hwstats->netdevice_nb.notifier_call = nsim_dev_netdevice_event;
+	err = register_netdevice_notifier_net(net, &hwstats->netdevice_nb);
+	if (err)
+		goto err_mutex_destroy;
+
+	hwstats->ddir = debugfs_create_dir("hwstats", nsim_dev->ddir);
+	if (IS_ERR(hwstats->ddir)) {
+		err = PTR_ERR(hwstats->ddir);
+		goto err_unregister_notifier;
+	}
+
+	hwstats->l3_ddir = debugfs_create_dir("l3", hwstats->ddir);
+	if (IS_ERR(hwstats->l3_ddir)) {
+		err = PTR_ERR(hwstats->l3_ddir);
+		goto err_remove_hwstats_recursive;
+	}
+
+	debugfs_create_file("enable_ifindex", 0600, hwstats->l3_ddir, hwstats,
+			    &nsim_dev_hwstats_l3_enable_fops.fops);
+	debugfs_create_file("disable_ifindex", 0600, hwstats->l3_ddir, hwstats,
+			    &nsim_dev_hwstats_l3_disable_fops.fops);
+	debugfs_create_file("fail_next_enable", 0600, hwstats->l3_ddir, hwstats,
+			    &nsim_dev_hwstats_l3_fail_fops.fops);
+
+	INIT_DELAYED_WORK(&hwstats->traffic_dw,
+			  &nsim_dev_hwstats_traffic_work);
+	schedule_delayed_work(&hwstats->traffic_dw,
+			      msecs_to_jiffies(NSIM_DEV_HWSTATS_TRAFFIC_MS));
+	return 0;
+
+err_remove_hwstats_recursive:
+	debugfs_remove_recursive(hwstats->ddir);
+err_unregister_notifier:
+	unregister_netdevice_notifier_net(net, &hwstats->netdevice_nb);
+err_mutex_destroy:
+	mutex_destroy(&hwstats->hwsdev_list_lock);
+	return err;
+}
+
+static void nsim_dev_hwsdev_list_wipe(struct nsim_dev_hwstats *hwstats,
+				      enum netdev_offload_xstats_type type)
+{
+	struct nsim_dev_hwstats_netdev *hwsdev, *tmp;
+	struct list_head *hwsdev_list;
+
+	hwsdev_list = nsim_dev_hwstats_get_list_head(hwstats, type);
+	if (WARN_ON(!hwsdev_list))
+		return;
+
+	mutex_lock(&hwstats->hwsdev_list_lock);
+	list_for_each_entry_safe(hwsdev, tmp, hwsdev_list, list) {
+		list_del(&hwsdev->list);
+		nsim_dev_hwsdev_fini(hwsdev);
+	}
+	mutex_unlock(&hwstats->hwsdev_list_lock);
+}
+
+void nsim_dev_hwstats_exit(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_hwstats *hwstats = &nsim_dev->hwstats;
+	struct net *net = nsim_dev_net(nsim_dev);
+
+	cancel_delayed_work_sync(&hwstats->traffic_dw);
+	debugfs_remove_recursive(hwstats->ddir);
+	unregister_netdevice_notifier_net(net, &hwstats->netdevice_nb);
+	nsim_dev_hwsdev_list_wipe(hwstats, NETDEV_OFFLOAD_XSTATS_TYPE_L3);
+	mutex_destroy(&hwstats->hwsdev_list_lock);
+}

drivers/net/netdevsim/netdevsim.h

@@ -184,6 +184,28 @@ struct nsim_dev_health {
 int nsim_dev_health_init(struct nsim_dev *nsim_dev, struct devlink *devlink);
 void nsim_dev_health_exit(struct nsim_dev *nsim_dev);
 
+struct nsim_dev_hwstats_netdev {
+	struct list_head list;
+	struct net_device *netdev;
+	struct rtnl_hw_stats64 stats;
+	bool enabled;
+	bool fail_enable;
+};
+
+struct nsim_dev_hwstats {
+	struct dentry *ddir;
+	struct dentry *l3_ddir;
+
+	struct mutex hwsdev_list_lock; /* protects hwsdev list(s) */
+	struct list_head l3_list;
+
+	struct notifier_block netdevice_nb;
+	struct delayed_work traffic_dw;
+};
+
+int nsim_dev_hwstats_init(struct nsim_dev *nsim_dev);
+void nsim_dev_hwstats_exit(struct nsim_dev *nsim_dev);
+
 #if IS_ENABLED(CONFIG_PSAMPLE)
 int nsim_dev_psample_init(struct nsim_dev *nsim_dev);
 void nsim_dev_psample_exit(struct nsim_dev *nsim_dev);
@@ -261,6 +283,7 @@ struct nsim_dev {
 	bool fail_reload;
 	struct devlink_region *dummy_region;
 	struct nsim_dev_health health;
+	struct nsim_dev_hwstats hwstats;
 	struct flow_action_cookie *fa_cookie;
 	spinlock_t fa_cookie_lock; /* protects fa_cookie */
 	bool fail_trap_group_set;

tools/testing/selftests/drivers/net/mlxsw/hw_stats_l3.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+lib_dir=$(dirname $0)/../../../net/forwarding
+
+ALL_TESTS="
+	l3_monitor_test
+"
+NUM_NETIFS=0
+source $lib_dir/lib.sh
+
+swp=$NETIF_NO_CABLE
+
+cleanup()
+{
+	pre_cleanup
+}
+
+l3_monitor_test()
+{
+	hw_stats_monitor_test $swp l3		    \
+		"ip addr add dev $swp 192.0.2.1/28" \
+		"ip addr del dev $swp 192.0.2.1/28"
+}
+
+trap cleanup EXIT
+
+setup_wait
+tests_run
+
+exit $EXIT_STATUS

tools/testing/selftests/drivers/net/netdevsim/hw_stats_l3.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+lib_dir=$(dirname $0)/../../../net/forwarding
+
+ALL_TESTS="
+	l3_reporting_test
+	l3_fail_next_test
+	l3_counter_test
+	l3_rollback_test
+	l3_monitor_test
+"
+
+NETDEVSIM_PATH=/sys/bus/netdevsim/
+DEV_ADDR_1=1337
+DEV_ADDR_2=1057
+DEV_ADDR_3=5417
+NUM_NETIFS=0
+source $lib_dir/lib.sh
+
+DUMMY_IFINDEX=
+
+DEV_ADDR()
+{
+	local n=$1; shift
+	local var=DEV_ADDR_$n
+
+	echo ${!var}
+}
+
+DEV()
+{
+	echo netdevsim$(DEV_ADDR $1)
+}
+
+DEVLINK_DEV()
+{
+	echo netdevsim/$(DEV $1)
+}
+
+SYSFS_NET_DIR()
+{
+	echo /sys/bus/netdevsim/devices/$(DEV $1)/net/
+}
+
+DEBUGFS_DIR()
+{
+	echo /sys/kernel/debug/netdevsim/$(DEV $1)/
+}
+
+nsim_add()
+{
+	local n=$1; shift
+
+	echo "$(DEV_ADDR $n) 1" > ${NETDEVSIM_PATH}/new_device
+	while [ ! -d $(SYSFS_NET_DIR $n) ] ; do :; done
+}
+
+nsim_reload()
+{
+	local n=$1; shift
+	local ns=$1; shift
+
+	devlink dev reload $(DEVLINK_DEV $n) netns $ns
+
+	if [ $? -ne 0 ]; then
+		echo "Failed to reload $(DEV $n) into netns \"testns1\""
+		exit 1
+	fi
+
+}
+
+nsim_del()
+{
+	local n=$1; shift
+
+	echo "$(DEV_ADDR $n)" > ${NETDEVSIM_PATH}/del_device
+}
+
+nsim_hwstats_toggle()
+{
+	local action=$1; shift
+	local instance=$1; shift
+	local netdev=$1; shift
+	local type=$1; shift
+
+	local ifindex=$($IP -j link show dev $netdev | jq '.[].ifindex')
+
+	echo $ifindex > $(DEBUGFS_DIR $instance)/hwstats/$type/$action
+}
+
+nsim_hwstats_enable()
+{
+	nsim_hwstats_toggle enable_ifindex "$@"
+}
+
+nsim_hwstats_disable()
+{
+	nsim_hwstats_toggle disable_ifindex "$@"
+}
+
+nsim_hwstats_fail_next_enable()
+{
+	nsim_hwstats_toggle fail_next_enable "$@"
+}
+
+setup_prepare()
+{
+	modprobe netdevsim &> /dev/null
+	nsim_add 1
+	nsim_add 2
+	nsim_add 3
+
+	ip netns add testns1
+
+	if [ $? -ne 0 ]; then
+		echo "Failed to add netns \"testns1\""
+		exit 1
+	fi
+
+	nsim_reload 1 testns1
+	nsim_reload 2 testns1
+	nsim_reload 3 testns1
+
+	IP="ip -n testns1"
+
+	$IP link add name dummy1 type dummy
+	$IP link set dev dummy1 up
+	DUMMY_IFINDEX=$($IP -j link show dev dummy1 | jq '.[].ifindex')
+}
+
+cleanup()
+{
+	pre_cleanup
+
+	$IP link del name dummy1
+	ip netns del testns1
+	nsim_del 3
+	nsim_del 2
+	nsim_del 1
+	modprobe -r netdevsim &> /dev/null
+}
+
+netdev_hwstats_used()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	$IP -j stats show dev "$netdev" group offload subgroup hw_stats_info |
+	    jq '.[].info.l3_stats.used'
+}
+
+netdev_check_used()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	[[ $(netdev_hwstats_used $netdev $type) == "true" ]]
+}
+
+netdev_check_unused()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	[[ $(netdev_hwstats_used $netdev $type) == "false" ]]
+}
+
+netdev_hwstats_request()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	$IP -j stats show dev "$netdev" group offload subgroup hw_stats_info |
+	    jq ".[].info.${type}_stats.request"
+}
+
+netdev_check_requested()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	[[ $(netdev_hwstats_request $netdev $type) == "true" ]]
+}
+
+netdev_check_unrequested()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+
+	[[ $(netdev_hwstats_request $netdev $type) == "false" ]]
+}
+
+reporting_test()
+{
+	local type=$1; shift
+	local instance=1
+
+	RET=0
+
+	[[ -n $(netdev_hwstats_used dummy1 $type) ]]
+	check_err $? "$type stats not reported"
+
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used before either device or netdevsim request"
+
+	nsim_hwstats_enable $instance dummy1 $type
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used before device request"
+	netdev_check_unrequested dummy1 $type
+	check_err $? "$type stats reported as requested before device request"
+
+	$IP stats set dev dummy1 ${type}_stats on
+	netdev_check_used dummy1 $type
+	check_err $? "$type stats reported as not used after both device and netdevsim request"
+	netdev_check_requested dummy1 $type
+	check_err $? "$type stats reported as not requested after device request"
+
+	nsim_hwstats_disable $instance dummy1 $type
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used after netdevsim request withdrawn"
+
+	nsim_hwstats_enable $instance dummy1 $type
+	netdev_check_used dummy1 $type
+	check_err $? "$type stats reported as not used after netdevsim request reenabled"
+
+	$IP stats set dev dummy1 ${type}_stats off
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used after device request withdrawn"
+	netdev_check_unrequested dummy1 $type
+	check_err $? "$type stats reported as requested after device request withdrawn"
+
+	nsim_hwstats_disable $instance dummy1 $type
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used after both requests withdrawn"
+
+	log_test "Reporting of $type stats usage"
+}
+
+l3_reporting_test()
+{
+	reporting_test l3
+}
+
+__fail_next_test()
+{
+	local instance=$1; shift
+	local type=$1; shift
+
+	RET=0
+
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used before either device or netdevsim request"
+
+	nsim_hwstats_enable $instance dummy1 $type
+	nsim_hwstats_fail_next_enable $instance dummy1 $type
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used before device request"
+	netdev_check_unrequested dummy1 $type
+	check_err $? "$type stats reported as requested before device request"
+
+	$IP stats set dev dummy1 ${type}_stats on 2>/dev/null
+	check_fail $? "$type stats request not bounced as it should have been"
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used after bounce"
+	netdev_check_unrequested dummy1 $type
+	check_err $? "$type stats reported as requested after bounce"
+
+	$IP stats set dev dummy1 ${type}_stats on
+	check_err $? "$type stats request failed when it shouldn't have"
+	netdev_check_used dummy1 $type
+	check_err $? "$type stats reported as not used after both device and netdevsim request"
+	netdev_check_requested dummy1 $type
+	check_err $? "$type stats reported as not requested after device request"
+
+	$IP stats set dev dummy1 ${type}_stats off
+	nsim_hwstats_disable $instance dummy1 $type
+
+	log_test "Injected failure of $type stats enablement (netdevsim #$instance)"
+}
+
+fail_next_test()
+{
+	__fail_next_test 1 "$@"
+	__fail_next_test 2 "$@"
+	__fail_next_test 3 "$@"
+}
+
+l3_fail_next_test()
+{
+	fail_next_test l3
+}
+
+get_hwstat()
+{
+	local netdev=$1; shift
+	local type=$1; shift
+	local selector=$1; shift
+
+	$IP -j stats show dev $netdev group offload subgroup ${type}_stats |
+		  jq ".[0].stats64.${selector}"
+}
+
+counter_test()
+{
+	local type=$1; shift
+	local instance=1
+
+	RET=0
+
+	nsim_hwstats_enable $instance dummy1 $type
+	$IP stats set dev dummy1 ${type}_stats on
+	netdev_check_used dummy1 $type
+	check_err $? "$type stats reported as not used after both device and netdevsim request"
+
+	# Netdevsim counts 10pps on ingress. We should see maybe a couple
+	# packets, unless things take a reeealy long time.
+	local pkts=$(get_hwstat dummy1 l3 rx.packets)
+	((pkts < 10))
+	check_err $? "$type stats show >= 10 packets after first enablement"
+
+	sleep 2
+
+	local pkts=$(get_hwstat dummy1 l3 rx.packets)
+	((pkts >= 20))
+	check_err $? "$type stats show < 20 packets after 2s passed"
+
+	$IP stats set dev dummy1 ${type}_stats off
+
+	sleep 2
+
+	$IP stats set dev dummy1 ${type}_stats on
+	local pkts=$(get_hwstat dummy1 l3 rx.packets)
+	((pkts < 10))
+	check_err $? "$type stats show >= 10 packets after second enablement"
+
+	$IP stats set dev dummy1 ${type}_stats off
+	nsim_hwstats_fail_next_enable $instance dummy1 $type
+	$IP stats set dev dummy1 ${type}_stats on 2>/dev/null
+	check_fail $? "$type stats request not bounced as it should have been"
+
+	sleep 2
+
+	$IP stats set dev dummy1 ${type}_stats on
+	local pkts=$(get_hwstat dummy1 l3 rx.packets)
+	((pkts < 10))
+	check_err $? "$type stats show >= 10 packets after post-fail enablement"
+
+	$IP stats set dev dummy1 ${type}_stats off
+
+	log_test "Counter values in $type stats"
+}
+
+l3_counter_test()
+{
+	counter_test l3
+}
+
+rollback_test()
+{
+	local type=$1; shift
+
+	RET=0
+
+	nsim_hwstats_enable 1 dummy1 l3
+	nsim_hwstats_enable 2 dummy1 l3
+	nsim_hwstats_enable 3 dummy1 l3
+
+	# The three netdevsim instances are registered in order of their number
+	# one after another. It is reasonable to expect that whatever
+	# notifications take place hit no. 2 in between hitting nos. 1 and 3,
+	# whatever the actual order. This allows us to test that a fail caused
+	# by no. 2 does not leave the system in a partial state, and rolls
+	# everything back.
+
+	nsim_hwstats_fail_next_enable 2 dummy1 l3
+	$IP stats set dev dummy1 ${type}_stats on 2>/dev/null
+	check_fail $? "$type stats request not bounced as it should have been"
+
+	netdev_check_unused dummy1 $type
+	check_err $? "$type stats reported as used after bounce"
+	netdev_check_unrequested dummy1 $type
+	check_err $? "$type stats reported as requested after bounce"
+
+	sleep 2
+
+	$IP stats set dev dummy1 ${type}_stats on
+	check_err $? "$type stats request not upheld as it should have been"
+
+	local pkts=$(get_hwstat dummy1 l3 rx.packets)
+	((pkts < 10))
+	check_err $? "$type stats show $pkts packets after post-fail enablement"
+
+	$IP stats set dev dummy1 ${type}_stats off
+
+	nsim_hwstats_disable 3 dummy1 l3
+	nsim_hwstats_disable 2 dummy1 l3
+	nsim_hwstats_disable 1 dummy1 l3
+
+	log_test "Failure in $type stats enablement rolled back"
+}
+
+l3_rollback_test()
+{
+	rollback_test l3
+}
+
+l3_monitor_test()
+{
+	hw_stats_monitor_test dummy1 l3		   \
+		"nsim_hwstats_enable 1 dummy1 l3"  \
+		"nsim_hwstats_disable 1 dummy1 l3" \
+		"$IP"
+}
+
+trap cleanup EXIT
+
+setup_prepare
+tests_run
+
+exit $EXIT_STATUS

tools/testing/selftests/net/forwarding/lib.sh

@@ -1498,3 +1498,63 @@ brmcast_check_sg_state()
 		check_err_fail $should_fail $? "Entry $src has blocked flag"
 	done
 }
+
+start_ip_monitor()
+{
+	local mtype=$1; shift
+	local ip=${1-ip}; shift
+
+	# start the monitor in the background
+	tmpfile=`mktemp /var/run/nexthoptestXXX`
+	mpid=`($ip monitor $mtype > $tmpfile & echo $!) 2>/dev/null`
+	sleep 0.2
+	echo "$mpid $tmpfile"
+}
+
+stop_ip_monitor()
+{
+	local mpid=$1; shift
+	local tmpfile=$1; shift
+	local el=$1; shift
+	local what=$1; shift
+
+	sleep 0.2
+	kill $mpid
+	local lines=`grep '^\w' $tmpfile | wc -l`
+	test $lines -eq $el
+	check_err $? "$what: $lines lines of events, expected $el"
+	rm -rf $tmpfile
+}
+
+hw_stats_monitor_test()
+{
+	local dev=$1; shift
+	local type=$1; shift
+	local make_suitable=$1; shift
+	local make_unsuitable=$1; shift
+	local ip=${1-ip}; shift
+
+	RET=0
+
+	# Expect a notification about enablement.
+	local ipmout=$(start_ip_monitor stats "$ip")
+	$ip stats set dev $dev ${type}_stats on
+	stop_ip_monitor $ipmout 1 "${type}_stats enablement"
+
+	# Expect a notification about offload.
+	local ipmout=$(start_ip_monitor stats "$ip")
+	$make_suitable
+	stop_ip_monitor $ipmout 1 "${type}_stats installation"
+
+	# Expect a notification about loss of offload.
+	local ipmout=$(start_ip_monitor stats "$ip")
+	$make_unsuitable
+	stop_ip_monitor $ipmout 1 "${type}_stats deinstallation"
+
+	# Expect a notification about disablement
+	local ipmout=$(start_ip_monitor stats "$ip")
+	$ip stats set dev $dev ${type}_stats off
+	stop_ip_monitor $ipmout 1 "${type}_stats disablement"
+
+	log_test "${type}_stats notifications"
+}