[PATCH net-next] openvswitch: enable ops lock for internal ports

[PATCH net-next] openvswitch: enable ops lock for internal ports

[Wang Zhan]

Open vSwitch internal ports currently use RTNL as their ops compatibility
lock. Opt them in to netdev instance locking so eligible control operations
can be serialized per device instead of contending on the global RTNL lock.

The internal port ethtool operations implement get_drvinfo and get_link.
The latter uses ethtool_op_get_link(), which synchronizes linkwatch state
and requires RTNL. Allow get_drvinfo to run under the instance lock, but
set ETHTOOL_OP_NEEDS_RTNL_GLINK to retain RTNL for get_link.

Feature synchronization can acquire a lower device's ops lock while holding
an internal port's lock. Assign these software upper devices a distinct
lockdep class to describe the nesting.

Signed-off-by: Wang Zhan <wang.zhan@smartx.com>
---
 net/openvswitch/vport-internal_dev.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
index 125d310871e93..eb2e83a3e16f1 100644
--- a/net/openvswitch/vport-internal_dev.c
+++ b/net/openvswitch/vport-internal_dev.c
@@ -11,6 +11,7 @@
 #include <linux/skbuff.h>
 
 #include <net/dst.h>
+#include <net/netdev_lock.h>
 #include <net/xfrm.h>
 #include <net/rtnetlink.h>
 
@@ -29,6 +30,12 @@ static struct internal_dev *internal_dev_priv(struct net_device *netdev)
 	return netdev_priv(netdev);
 }
 
+static int internal_dev_init(struct net_device *netdev)
+{
+	netdev_lockdep_set_classes(netdev);
+	return 0;
+}
+
 /* Called with rcu_read_lock_bh. */
 static netdev_tx_t
 internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)
@@ -69,6 +76,7 @@ static void internal_dev_getinfo(struct net_device *netdev,
 }
 
 static const struct ethtool_ops internal_dev_ethtool_ops = {
+	.op_needs_rtnl	= ETHTOOL_OP_NEEDS_RTNL_GLINK,
 	.get_drvinfo	= internal_dev_getinfo,
 	.get_link	= ethtool_op_get_link,
 };
@@ -81,6 +89,7 @@ static void internal_dev_destructor(struct net_device *dev)
 }
 
 static const struct net_device_ops internal_dev_netdev_ops = {
+	.ndo_init = internal_dev_init,
 	.ndo_open = internal_dev_open,
 	.ndo_stop = internal_dev_stop,
 	.ndo_start_xmit = internal_dev_xmit,
@@ -106,6 +115,7 @@ static void do_setup(struct net_device *netdev)
 	netdev->needs_free_netdev = true;
 	netdev->priv_destructor = NULL;
 	netdev->ethtool_ops = &internal_dev_ethtool_ops;
+	netdev->request_ops_lock = true;
 	netdev->rtnl_link_ops = &internal_dev_link_ops;
 
 	netdev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA |

base-commit: ac155a26750a595703e7dadff84735456d75a479
-- 
2.47.3

Re: [PATCH net-next] openvswitch: enable ops lock for internal ports

[Jakub Kicinski]

On Wed, 12 Aug 2026 20:30:03 +0800 Wang Zhan wrote:
> Open vSwitch internal ports currently use RTNL as their ops compatibility
> lock. Opt them in to netdev instance locking so eligible control operations
> can be serialized per device instead of contending on the global RTNL lock.
> 
> The internal port ethtool operations implement get_drvinfo and get_link.
> The latter uses ethtool_op_get_link(), which synchronizes linkwatch state
> and requires RTNL. Allow get_drvinfo to run under the instance lock, but
> set ETHTOOL_OP_NEEDS_RTNL_GLINK to retain RTNL for get_link.
> 
> Feature synchronization can acquire a lower device's ops lock while holding
> an internal port's lock. Assign these software upper devices a distinct
> lockdep class to describe the nesting.

Why are you sending this patch? Do you have an actual real life need
for unlocked get_drvinfo??

Re: [PATCH net-next] openvswitch: enable ops lock for internal ports

[Wang Zhan]

> Why are you sending this patch? Do you have an actual real life need
> for unlocked get_drvinfo??

Yes. The use case is broader than unlocked get_drvinfo.

We are trying to reduce cases where ovs-vswitchd gets blocked waiting for
the global RTNL lock. In production we saw ovs-vswitchd repeatedly report
"Unreasonably long" poll intervals. Tracing showed one OVS operation waiting
about 500 ms for RTNL while node-exporter was collecting the speed of an
mlx5 interface. The node-exporter process was CPU quota throttled, which
stretched that RTNL hold time; mlx5 can make this easier to hit because some
queries go through firmware/mailbox paths.

netdev_linux_set_ol() is one OVS path that can take RTNL. With
userspace-tso-enable, OVS uses this path to read ethtool feature information
through ETHTOOL_GSSET_INFO, ETHTOOL_GSTRINGS and ETHTOOL_GFEATURES. For
ovs-internal-port, these GET operations do not need RTNL, but currently take
it because internal ports do not opt into per-device ops locking.