netdev - [RFC PATCH v2 net-next 6/7] net: ethtool: add a mutex protecting RSS contexts

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Message-ID: <9e2bcb887b5cf9cbb8c0c4ba126115fe01a01f3f.1681236654.git.ecree.xilinx@gmail.com>
Date:   Tue, 11 Apr 2023 19:26:14 +0100
From:   <edward.cree@....com>
To:     <linux-net-drivers@....com>, <davem@...emloft.net>,
        <kuba@...nel.org>, <pabeni@...hat.com>, <edumazet@...gle.com>
CC:     Edward Cree <ecree.xilinx@...il.com>, <netdev@...r.kernel.org>,
        <habetsm.xilinx@...il.com>, <sudheer.mogilappagari@...el.com>
Subject: [RFC PATCH v2 net-next 6/7] net: ethtool: add a mutex protecting RSS contexts

From: Edward Cree <ecree.xilinx@...il.com>

While this is not needed to serialise the ethtool entry points (which
 are all under RTNL), drivers may have cause to asynchronously access
 dev->ethtool->rss_ctx; taking dev->ethtool->rss_lock allows them to
 do this safely without needing to take the RTNL.

Signed-off-by: Edward Cree <ecree.xilinx@...il.com>
---
 include/linux/ethtool.h | 3 +++
 net/core/dev.c          | 5 +++++
 net/ethtool/ioctl.c     | 7 +++++++
 3 files changed, 15 insertions(+)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 724da9234cf1..e8e88d5900d3 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -1026,11 +1026,14 @@ int ethtool_virtdev_set_link_ksettings(struct net_device *dev,
  * struct ethtool_netdev_state - per-netdevice state for ethtool features
  * @rss_ctx_max_id:	maximum (exclusive) supported RSS context ID
  * @rss_ctx:		IDR storing custom RSS context state
+ * @rss_lock:		Protects entries in @rss_ctx.  May be taken from
+ *			within RTNL.
  * @wol_enabled:	Wake-on-LAN is enabled
  */
 struct ethtool_netdev_state {
 	u32			rss_ctx_max_id;
 	struct idr		rss_ctx;
+	struct mutex		rss_lock;
 	unsigned		wol_enabled:1;
 };
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 44668386f376..60c844b372e3 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9987,6 +9987,7 @@ int register_netdevice(struct net_device *dev)
 	idr_init_base(&dev->ethtool->rss_ctx, 1);
 
 	spin_lock_init(&dev->addr_list_lock);
+	mutex_init(&dev->ethtool->rss_lock);
 	netdev_set_addr_lockdep_class(dev);
 
 	ret = dev_get_valid_name(net, dev, dev->name);
@@ -10792,6 +10793,7 @@ static void netdev_rss_contexts_free(struct net_device *dev)
 	if (!dev->ethtool_ops->create_rxfh_context &&
 	    !dev->ethtool_ops->set_rxfh_context)
 		return;
+	mutex_lock(&dev->ethtool->rss_lock);
 	idr_for_each_entry(&dev->ethtool->rss_ctx, ctx, context) {
 		u32 *indir = ethtool_rxfh_context_indir(ctx);
 		u8 *key = ethtool_rxfh_context_key(ctx);
@@ -10806,6 +10808,7 @@ static void netdev_rss_contexts_free(struct net_device *dev)
 							   &context, true);
 		kfree(ctx);
 	}
+	mutex_unlock(&dev->ethtool->rss_lock);
 }
 
 /**
@@ -10919,6 +10922,8 @@ void unregister_netdevice_many_notify(struct list_head *head,
 		if (dev->netdev_ops->ndo_uninit)
 			dev->netdev_ops->ndo_uninit(dev);
 
+		mutex_destroy(&dev->ethtool->rss_lock);
+
 		if (skb)
 			rtmsg_ifinfo_send(skb, dev, GFP_KERNEL, portid, nlh);
 
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index abd1cf50e681..8b2e90ba03a1 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1257,6 +1257,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	u8 *rss_config;
 	u32 rss_cfg_offset = offsetof(struct ethtool_rxfh, rss_config[0]);
 	bool create = false, delete = false;
+	bool locked = false; /* dev->ethtool->rss_lock taken */
 
 	if (!ops->get_rxnfc || !ops->set_rxfh)
 		return -EOPNOTSUPP;
@@ -1334,6 +1335,10 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 		}
 	}
 
+	if (rxfh.rss_context) {
+		mutex_lock(&dev->ethtool->rss_lock);
+		locked = true;
+	}
 	if (create) {
 		if (delete) {
 			ret = -EINVAL;
@@ -1453,6 +1458,8 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	}
 
 out:
+	if (locked)
+		mutex_unlock(&dev->ethtool->rss_lock);
 	kfree(rss_config);
 	return ret;
 }