Commit 03df156d authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

xdp: double protect netdev->xdp_flags with netdev->lock 



Protect xdp_features with netdev->lock. This way pure readers
no longer have to take rtnl_lock to access the field.

This includes calling NETDEV_XDP_FEAT_CHANGE under the lock.
Looks like that's fine for bonding, the only "real" listener,
it's the same as ethtool feature change.

In terms of normal drivers - only GVE need special consideration
(other drivers don't use instance lock or don't support XDP).
It calls xdp_set_features_flag() helper from gve_init_priv() which
in turn is called from gve_reset_recovery() (locked), or prior
to netdev registration. So switch to _locked.

Reviewed-by: default avatarJoe Damato <jdamato@fastly.com>
Acked-by: default avatarStanislav Fomichev <sdf@fomichev.me>
Acked-by: default avatarHarshitha Ramamurthy <hramamurthy@google.com>
Acked-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250408195956.412733-6-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d02e3b38

Documentation/networking/netdevices.rst

+1 −0
Original line number Diff line number Diff line
@@ -354,6 +354,7 @@ For devices with locked ops, currently only the following notifiers are 
running under the lock:

* ``NETDEV_REGISTER``

* ``NETDEV_UP``

* ``NETDEV_XDP_FEAT_CHANGE``



The following notifiers are running without the lock:

* ``NETDEV_UNREGISTER``

drivers/net/ethernet/google/gve/gve_main.c

+1 −1
Original line number Diff line number Diff line
@@ -2185,7 +2185,7 @@ static void gve_set_netdev_xdp_features(struct gve_priv *priv) 
		xdp_features = 0;

	}



	xdp_set_features_flag(priv->dev, xdp_features);

	xdp_set_features_flag_locked(priv->dev, xdp_features);

}



static int gve_init_priv(struct gve_priv *priv, bool skip_describe_device)

include/linux/netdevice.h

+1 −1
Original line number Diff line number Diff line
@@ -2526,7 +2526,7 @@ struct net_device { 
	 *	@net_shaper_hierarchy, @reg_state, @threaded

	 *

	 * Double protects:

	 *	@up, @moving_ns, @nd_net

	 *	@up, @moving_ns, @nd_net, @xdp_flags

	 *

	 * Double ops protects:

	 *	@real_num_rx_queues, @real_num_tx_queues

include/net/xdp.h

+1 −0
Original line number Diff line number Diff line
@@ -616,6 +616,7 @@ struct xdp_metadata_ops { 
u32 bpf_xdp_metadata_kfunc_id(int id);

bool bpf_dev_bound_kfunc_id(u32 btf_id);

void xdp_set_features_flag(struct net_device *dev, xdp_features_t val);

void xdp_set_features_flag_locked(struct net_device *dev, xdp_features_t val);

void xdp_features_set_redirect_target(struct net_device *dev, bool support_sg);

void xdp_features_clear_redirect_target(struct net_device *dev);

#else

net/core/lock_debug.c

+1 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ int netdev_debug_event(struct notifier_block *nb, unsigned long event, 
	switch (cmd) {

	case NETDEV_REGISTER:

	case NETDEV_UP:

	case NETDEV_XDP_FEAT_CHANGE:

		netdev_ops_assert_locked(dev);

		fallthrough;

	case NETDEV_DOWN:
@@ -58,7 +59,6 @@ int netdev_debug_event(struct notifier_block *nb, unsigned long event, 
	case NETDEV_OFFLOAD_XSTATS_DISABLE:

	case NETDEV_OFFLOAD_XSTATS_REPORT_USED:

	case NETDEV_OFFLOAD_XSTATS_REPORT_DELTA:

	case NETDEV_XDP_FEAT_CHANGE:

		ASSERT_RTNL();

		break;