net: ethtool: rss: add notifications

In preparation for RSS_SET handling in ethnl introduce Netlink
notifications for RSS. Only cover modifications, not creation
and not removal of a context, because the latter may deserve
a different notification type. We should cross that bridge
when we add the support for context add / remove via Netlink.

Link: https://patch.msgid.link/20250623231720.3124717-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

Documentation/netlink/specs/ethtool.yaml

@@ -2492,6 +2492,13 @@ operations:
         attributes:
           - header
           - events
+    -
+      name: rss-ntf
+      doc: |
+        Notification for change in RSS configuration.
+        For additional contexts only modifications are modified, not creation
+        or removal of the contexts.
+      notify: rss-get
 
 mcast-groups:
   list:

Documentation/networking/ethtool-netlink.rst

@@ -281,6 +281,7 @@ Kernel to userspace:
   ``ETHTOOL_MSG_MODULE_GET_REPLY``         transceiver module parameters
   ``ETHTOOL_MSG_PSE_GET_REPLY``            PSE parameters
   ``ETHTOOL_MSG_RSS_GET_REPLY``            RSS settings
+  ``ETHTOOL_MSG_RSS_NTF``                  RSS settings
   ``ETHTOOL_MSG_PLCA_GET_CFG_REPLY``       PLCA RS parameters
   ``ETHTOOL_MSG_PLCA_GET_STATUS_REPLY``    PLCA RS status
   ``ETHTOOL_MSG_PLCA_NTF``                 PLCA RS parameters

include/uapi/linux/ethtool_netlink_generated.h

@@ -862,6 +862,7 @@ enum {
 	ETHTOOL_MSG_TSCONFIG_GET_REPLY,
 	ETHTOOL_MSG_TSCONFIG_SET_REPLY,
 	ETHTOOL_MSG_PSE_NTF,
+	ETHTOOL_MSG_RSS_NTF,
 
 	__ETHTOOL_MSG_KERNEL_CNT,
 	ETHTOOL_MSG_KERNEL_MAX = (__ETHTOOL_MSG_KERNEL_CNT - 1)

net/ethtool/common.h

@@ -74,4 +74,12 @@ int ethtool_get_module_eeprom_call(struct net_device *dev,
 
 bool __ethtool_dev_mm_supported(struct net_device *dev);
 
+#if IS_ENABLED(CONFIG_ETHTOOL_NETLINK)
+void ethtool_rss_notify(struct net_device *dev, u32 rss_context);
+#else
+static inline void ethtool_rss_notify(struct net_device *dev, u32 rss_context)
+{
+}
+#endif
+
 #endif /* _ETHTOOL_COMMON_H */

net/ethtool/ioctl.c

@@ -1502,6 +1502,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	struct ethtool_rxfh rxfh;
 	bool locked = false; /* dev->ethtool->rss_lock taken */
 	bool create = false;
+	bool mod = false;
 	u8 *rss_config;
 	int ret;
 
@@ -1688,6 +1689,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 		}
 		goto out;
 	}
+	mod = !create && !rxfh_dev.rss_delete;
 
 	if (copy_to_user(useraddr + offsetof(struct ethtool_rxfh, rss_context),
 			 &rxfh_dev.rss_context, sizeof(rxfh_dev.rss_context)))
@@ -1757,6 +1759,8 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	if (locked)
 		mutex_unlock(&dev->ethtool->rss_lock);
 	kfree(rss_config);
+	if (mod)
+		ethtool_rss_notify(dev, rxfh.rss_context);
 	return ret;
 }
 

net/ethtool/netlink.c

@@ -946,6 +946,7 @@ ethnl_default_notify_ops[ETHTOOL_MSG_KERNEL_MAX + 1] = {
 	[ETHTOOL_MSG_MODULE_NTF]	= &ethnl_module_request_ops,
 	[ETHTOOL_MSG_PLCA_NTF]		= &ethnl_plca_cfg_request_ops,
 	[ETHTOOL_MSG_MM_NTF]		= &ethnl_mm_request_ops,
+	[ETHTOOL_MSG_RSS_NTF]		= &ethnl_rss_request_ops,
 };
 
 /* default notification handler */
@@ -1052,6 +1053,7 @@ static const ethnl_notify_handler_t ethnl_notify_handlers[] = {
 	[ETHTOOL_MSG_MODULE_NTF]	= ethnl_default_notify,
 	[ETHTOOL_MSG_PLCA_NTF]		= ethnl_default_notify,
 	[ETHTOOL_MSG_MM_NTF]		= ethnl_default_notify,
+	[ETHTOOL_MSG_RSS_NTF]		= ethnl_default_notify,
 };
 
 void ethnl_notify(struct net_device *dev, unsigned int cmd,

net/ethtool/rss.c

@@ -358,6 +358,17 @@ int ethnl_rss_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 	return ret;
 }
 
+/* RSS_NTF */
+
+void ethtool_rss_notify(struct net_device *dev, u32 rss_context)
+{
+	struct rss_req_info req_info = {
+		.rss_context = rss_context,
+	};
+
+	ethnl_notify(dev, ETHTOOL_MSG_RSS_NTF, &req_info.base);
+}
+
 const struct ethnl_request_ops ethnl_rss_request_ops = {
 	.request_cmd		= ETHTOOL_MSG_RSS_GET,
 	.reply_cmd		= ETHTOOL_MSG_RSS_GET_REPLY,