[PATCH net-next v3 0/2] Allow disabling pause frames on panic

[PATCH net-next v3 0/2] Allow disabling pause frames on panic

[Florian Fainelli]

This patch set allows disabling pause frame generation upon encountering
a kernel panic. This has proven to be helpful in lab environments where
devices are still being worked on, will panic for various reasons, and
will occasionally take down the entire Ethernet switch they are attached
to.

Changes in v3:

- early feedback as to whether we can disable pause on panic
- correct documentation
- simplify network device list traversal
- only need to disable pause frame generation (TX)

Changes in v2:

- introduce a dedicated callback that runs in panic context

Florian Fainelli (2):
  net: ethernet: Allow disabling pause on panic
  net: bcmgenet: Add support for set_pauseparam_panic

 Documentation/ABI/testing/sysfs-class-net     | 16 ++++
 .../net/ethernet/broadcom/genet/bcmgenet.c    |  8 ++
 .../net/ethernet/broadcom/genet/bcmgenet.h    |  1 +
 drivers/net/ethernet/broadcom/genet/bcmmii.c  | 10 +++
 include/linux/ethtool.h                       |  3 +
 include/linux/netdevice.h                     |  1 +
 net/core/net-sysfs.c                          | 39 +++++++++
 net/ethernet/Makefile                         |  3 +-
 net/ethernet/pause_panic.c                    | 79 +++++++++++++++++++
 9 files changed, 159 insertions(+), 1 deletion(-)
 create mode 100644 net/ethernet/pause_panic.c

-- 
2.34.1

[PATCH net-next v3 1/2] net: ethernet: Allow disabling pause on panic

[Florian Fainelli]

Development devices on a lab network might be subject to kernel panics
and if they have pause frame generation enabled, once the kernel panics,
the Ethernet controller stops being serviced. This can create a flood of
pause frames that certain switches are unable to handle resulting a
completle paralysis of the network because they broadcast to other
stations on that same network segment.

To accomodate for such situation introduce a
/sys/class/net/<device>/disable_pause_on_panic knob which will disable
Ethernet pause frame generation upon kernel panic.

Note that device driver wishing to make use of that feature need to
implement ethtool_ops::set_pauseparam_panic to specifically deal with
that atomic context.

Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 Documentation/ABI/testing/sysfs-class-net | 16 +++++
 include/linux/ethtool.h                   |  3 +
 include/linux/netdevice.h                 |  1 +
 net/core/net-sysfs.c                      | 39 +++++++++++
 net/ethernet/Makefile                     |  3 +-
 net/ethernet/pause_panic.c                | 79 +++++++++++++++++++++++
 6 files changed, 140 insertions(+), 1 deletion(-)
 create mode 100644 net/ethernet/pause_panic.c

diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
index ebf21beba846..da0e4e862aca 100644
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -352,3 +352,19 @@ Description:
 		0  threaded mode disabled for this dev
 		1  threaded mode enabled for this dev
 		== ==================================
+
+What:		/sys/class/net/<iface>/disable_pause_on_panic
+Date:		Nov 2025
+KernelVersion:	6.20
+Contact:	netdev@vger.kernel.org
+Description:
+		Boolean value to control whether to disable pause frame
+		generation on panic. This is helpful in environments where
+		the link partner may incorrect respond to pause frames (e.g.:
+		improperly configured Ethernet switches)
+
+		Possible values:
+		== =====================================================
+		0  do not disable pause frame generation on kernel panic
+		1  disable pause frame generation on kernel panic
+		== =====================================================
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index c2d8b4ec62eb..e014d0f2a5ac 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -956,6 +956,8 @@ struct kernel_ethtool_ts_info {
  * @get_pauseparam: Report pause parameters
  * @set_pauseparam: Set pause parameters.  Returns a negative error code
  *	or zero.
+ * @set_pauseparam_panic: Set pause parameters while in a panic context. This
+ *	call is not allowed to sleep. Returns a negative error code or zero.
  * @self_test: Run specified self-tests
  * @get_strings: Return a set of strings that describe the requested objects
  * @set_phys_id: Identify the physical devices, e.g. by flashing an LED
@@ -1170,6 +1172,7 @@ struct ethtool_ops {
 				  struct ethtool_pauseparam*);
 	int	(*set_pauseparam)(struct net_device *,
 				  struct ethtool_pauseparam*);
+	void	(*set_pauseparam_panic)(struct net_device *);
 	void	(*self_test)(struct net_device *, struct ethtool_test *, u64 *);
 	void	(*get_strings)(struct net_device *, u32 stringset, u8 *);
 	int	(*set_phys_id)(struct net_device *, enum ethtool_phys_id_state);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e808071dbb7d..2d4b07693745 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2441,6 +2441,7 @@ struct net_device {
 	bool			proto_down;
 	bool			irq_affinity_auto;
 	bool			rx_cpu_rmap_auto;
+	bool			disable_pause_on_panic;
 
 	/* priv_flags_slow, ungrouped to save space */
 	unsigned long		see_all_hwtstamp_requests:1;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ca878525ad7c..a752163ded8c 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -770,6 +770,44 @@ static ssize_t threaded_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(threaded);
 
+static ssize_t disable_pause_on_panic_show(struct device *dev,
+					    struct device_attribute *attr,
+					    char *buf)
+{
+	struct net_device *ndev = to_net_dev(dev);
+	ssize_t ret = -EINVAL;
+
+	rcu_read_lock();
+	if (dev_isalive(ndev))
+		ret = sysfs_emit(buf, fmt_dec, READ_ONCE(ndev->disable_pause_on_panic));
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int modify_disable_pause_on_panic(struct net_device *dev, unsigned long val)
+{
+	const struct ethtool_ops *ops = dev->ethtool_ops;
+
+	if (!ops || !ops->set_pauseparam_panic)
+		return -EOPNOTSUPP;
+
+	if (val != 0 && val != 1)
+		return -EINVAL;
+
+	WRITE_ONCE(dev->disable_pause_on_panic, val);
+
+	return 0;
+}
+
+static ssize_t disable_pause_on_panic_store(struct device *dev,
+					     struct device_attribute *attr,
+					     const char *buf, size_t len)
+{
+	return netdev_store(dev, attr, buf, len, modify_disable_pause_on_panic);
+}
+static DEVICE_ATTR_RW(disable_pause_on_panic);
+
 static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_netdev_group.attr,
 	&dev_attr_type.attr,
@@ -800,6 +838,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_carrier_up_count.attr,
 	&dev_attr_carrier_down_count.attr,
 	&dev_attr_threaded.attr,
+	&dev_attr_disable_pause_on_panic.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(net_class);
diff --git a/net/ethernet/Makefile b/net/ethernet/Makefile
index e03eff94e0db..9b1f3ff8695a 100644
--- a/net/ethernet/Makefile
+++ b/net/ethernet/Makefile
@@ -3,4 +3,5 @@
 # Makefile for the Linux Ethernet layer.
 #
 
-obj-y					+= eth.o
+obj-y					+= eth.o \
+					   pause_panic.o
diff --git a/net/ethernet/pause_panic.c b/net/ethernet/pause_panic.c
new file mode 100644
index 000000000000..2a4960c5f261
--- /dev/null
+++ b/net/ethernet/pause_panic.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ethernet pause disable on panic handler
+ *
+ * This module provides per-device control via sysfs to disable Ethernet flow
+ * control (pause frames) on individual Ethernet devices when the kernel panics.
+ * Each device can be configured via /sys/class/net/<device>/disable_pause_on_panic.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/panic_notifier.h>
+#include <linux/netdevice.h>
+#include <linux/ethtool.h>
+#include <linux/notifier.h>
+#include <linux/if_ether.h>
+#include <net/net_namespace.h>
+
+/*
+ * Disable pause/flow control on a single Ethernet device.
+ */
+static void disable_pause_on_device(struct net_device *dev)
+{
+	const struct ethtool_ops *ops;
+
+	/* Only proceed if this device has the flag enabled */
+	if (!READ_ONCE(dev->disable_pause_on_panic))
+		return;
+
+	ops = dev->ethtool_ops;
+	if (!ops || !ops->set_pauseparam_panic)
+		return;
+
+	/*
+	 * In panic context, we're in atomic context and cannot sleep.
+	 */
+	ops->set_pauseparam_panic(dev);
+}
+
+/*
+ * Panic notifier to disable pause frames on all Ethernet devices.
+ * Called in atomic context during kernel panic.
+ */
+static int eth_pause_panic_handler(struct notifier_block *this,
+					unsigned long event, void *ptr)
+{
+	struct net_device *dev;
+
+	/*
+	 * Iterate over all network devices in the init namespace.
+	 * In panic context, we cannot acquire locks that might sleep,
+	 * so we use RCU iteration.
+	 * Each device will check its own disable_pause_on_panic flag.
+	 */
+	for_each_netdev(&init_net, dev) {
+		/* Reference count might not be available in panic */
+		if (!dev)
+			continue;
+
+		disable_pause_on_device(dev);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block eth_pause_panic_notifier = {
+	.notifier_call = eth_pause_panic_handler,
+	.priority = INT_MAX, /* Run as late as possible */
+};
+
+static int __init eth_pause_panic_init(void)
+{
+	/* Register panic notifier */
+	atomic_notifier_chain_register(&panic_notifier_list,
+				       &eth_pause_panic_notifier);
+
+	return 0;
+}
+device_initcall(eth_pause_panic_init);
-- 
2.34.1

Re: [PATCH net-next v3 1/2] net: ethernet: Allow disabling pause on panic

[Jakub Kicinski]

On Thu,  6 Nov 2025 16:25:09 -0800 Florian Fainelli wrote:
> Development devices on a lab network might be subject to kernel panics
> and if they have pause frame generation enabled, once the kernel panics,
> the Ethernet controller stops being serviced. This can create a flood of
> pause frames that certain switches are unable to handle resulting a
> completle paralysis of the network because they broadcast to other
> stations on that same network segment.
> 
> To accomodate for such situation introduce a
> /sys/class/net/<device>/disable_pause_on_panic knob which will disable
> Ethernet pause frame generation upon kernel panic.
> 
> Note that device driver wishing to make use of that feature need to
> implement ethtool_ops::set_pauseparam_panic to specifically deal with
> that atomic context.

Some basic review comments below (no promises if addressing those will
make me for one feel any warmer towards the concept).

>  Documentation/ABI/testing/sysfs-class-net | 16 +++++
>  include/linux/ethtool.h                   |  3 +
>  include/linux/netdevice.h                 |  1 +
>  net/core/net-sysfs.c                      | 39 +++++++++++
>  net/ethernet/Makefile                     |  3 +-
>  net/ethernet/pause_panic.c                | 79 +++++++++++++++++++++++

panic.c or shutdown.c is probably a slightly better name,
more likely we'd add more code in that.

>  6 files changed, 140 insertions(+), 1 deletion(-)
>  create mode 100644 net/ethernet/pause_panic.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
> index ebf21beba846..da0e4e862aca 100644
> --- a/Documentation/ABI/testing/sysfs-class-net
> +++ b/Documentation/ABI/testing/sysfs-class-net
> @@ -352,3 +352,19 @@ Description:
>  		0  threaded mode disabled for this dev
>  		1  threaded mode enabled for this dev
>  		== ==================================
> +
> +What:		/sys/class/net/<iface>/disable_pause_on_panic
> +Date:		Nov 2025
> +KernelVersion:	6.20
> +Contact:	netdev@vger.kernel.org
> +Description:
> +		Boolean value to control whether to disable pause frame
> +		generation on panic. This is helpful in environments where
> +		the link partner may incorrect respond to pause frames (e.g.:
> +		improperly configured Ethernet switches)
> +
> +		Possible values:
> +		== =====================================================
> +		0  do not disable pause frame generation on kernel panic
> +		1  disable pause frame generation on kernel panic
> +		== =====================================================

please no sysfs for something as niche as this feature

> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index e808071dbb7d..2d4b07693745 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -2441,6 +2441,7 @@ struct net_device {
>  	bool			proto_down;
>  	bool			irq_affinity_auto;
>  	bool			rx_cpu_rmap_auto;
> +	bool			disable_pause_on_panic;

Warning: include/linux/netdevice.h:2567 struct member
'disable_pause_on_panic' not described in 'net_device'

>  	/* priv_flags_slow, ungrouped to save space */
>  	unsigned long		see_all_hwtstamp_requests:1;

> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/panic_notifier.h>
> +#include <linux/netdevice.h>
> +#include <linux/ethtool.h>
> +#include <linux/notifier.h>
> +#include <linux/if_ether.h>
> +#include <net/net_namespace.h>

Alphabetical sort, please.

> +/*
> + * Disable pause/flow control on a single Ethernet device.
> + */
> +static void disable_pause_on_device(struct net_device *dev)
> +{
> +	const struct ethtool_ops *ops;
> +
> +	/* Only proceed if this device has the flag enabled */
> +	if (!READ_ONCE(dev->disable_pause_on_panic))
> +		return;
> +
> +	ops = dev->ethtool_ops;
> +	if (!ops || !ops->set_pauseparam_panic)
> +		return;
> +
> +	/*
> +	 * In panic context, we're in atomic context and cannot sleep.
> +	 */

single-line comment would do?

> +	ops->set_pauseparam_panic(dev);
> +}
-- 
pw-bot: cr

Re: [PATCH net-next v3 1/2] net: ethernet: Allow disabling pause on panic

[Florian Fainelli]

On 11/10/25 17:10, Jakub Kicinski wrote:
> On Thu,  6 Nov 2025 16:25:09 -0800 Florian Fainelli wrote:
>> Development devices on a lab network might be subject to kernel panics
>> and if they have pause frame generation enabled, once the kernel panics,
>> the Ethernet controller stops being serviced. This can create a flood of
>> pause frames that certain switches are unable to handle resulting a
>> completle paralysis of the network because they broadcast to other
>> stations on that same network segment.
>>
>> To accomodate for such situation introduce a
>> /sys/class/net/<device>/disable_pause_on_panic knob which will disable
>> Ethernet pause frame generation upon kernel panic.
>>
>> Note that device driver wishing to make use of that feature need to
>> implement ethtool_ops::set_pauseparam_panic to specifically deal with
>> that atomic context.
> 
> Some basic review comments below (no promises if addressing those will
> make me for one feel any warmer towards the concept).
> 
>>   Documentation/ABI/testing/sysfs-class-net | 16 +++++
>>   include/linux/ethtool.h                   |  3 +
>>   include/linux/netdevice.h                 |  1 +
>>   net/core/net-sysfs.c                      | 39 +++++++++++
>>   net/ethernet/Makefile                     |  3 +-
>>   net/ethernet/pause_panic.c                | 79 +++++++++++++++++++++++
> 
> panic.c or shutdown.c is probably a slightly better name,
> more likely we'd add more code in that.
> 
>>   6 files changed, 140 insertions(+), 1 deletion(-)
>>   create mode 100644 net/ethernet/pause_panic.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
>> index ebf21beba846..da0e4e862aca 100644
>> --- a/Documentation/ABI/testing/sysfs-class-net
>> +++ b/Documentation/ABI/testing/sysfs-class-net
>> @@ -352,3 +352,19 @@ Description:
>>   		0  threaded mode disabled for this dev
>>   		1  threaded mode enabled for this dev
>>   		== ==================================
>> +
>> +What:		/sys/class/net/<iface>/disable_pause_on_panic
>> +Date:		Nov 2025
>> +KernelVersion:	6.20
>> +Contact:	netdev@vger.kernel.org
>> +Description:
>> +		Boolean value to control whether to disable pause frame
>> +		generation on panic. This is helpful in environments where
>> +		the link partner may incorrect respond to pause frames (e.g.:
>> +		improperly configured Ethernet switches)
>> +
>> +		Possible values:
>> +		== =====================================================
>> +		0  do not disable pause frame generation on kernel panic
>> +		1  disable pause frame generation on kernel panic
>> +		== =====================================================
> 
> please no sysfs for something as niche as this feature

Would you prefer ethtool in that case?
-- 
Florian

Re: [PATCH net-next v3 1/2] net: ethernet: Allow disabling pause on panic

[Jakub Kicinski]

On Wed, 12 Nov 2025 14:53:51 -0800 Florian Fainelli wrote:
> > please no sysfs for something as niche as this feature  
> 
> Would you prefer ethtool in that case?

Yes, no strong preference where exactly but somewhere within ethtool
would be better.

[PATCH net-next v3 2/2] net: bcmgenet: Add support for set_pauseparam_panic

[Florian Fainelli]

Avoid making sleeping calls that would in not being able to complete the
MMIO writes ignoring pause frame reception and generation at the
Ethernet MAC controller level.

Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Change-Id: I268ffdaf28e6df30f37e2eaae421c06c727f524a
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c |  8 ++++++++
 drivers/net/ethernet/broadcom/genet/bcmgenet.h |  1 +
 drivers/net/ethernet/broadcom/genet/bcmmii.c   | 10 ++++++++++
 3 files changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index d99ef92feb82..323bf119c2af 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -966,6 +966,13 @@ static int bcmgenet_set_pauseparam(struct net_device *dev,
 	return 0;
 }
 
+static void bcmgenet_set_pauseparam_panic(struct net_device *dev)
+{
+	struct bcmgenet_priv *priv = netdev_priv(dev);
+
+	bcmgenet_set_pause_panic(priv);
+}
+
 /* standard ethtool support functions. */
 enum bcmgenet_stat_type {
 	BCMGENET_STAT_RTNL = -1,
@@ -1702,6 +1709,7 @@ static const struct ethtool_ops bcmgenet_ethtool_ops = {
 	.set_rxnfc		= bcmgenet_set_rxnfc,
 	.get_pauseparam		= bcmgenet_get_pauseparam,
 	.set_pauseparam		= bcmgenet_set_pauseparam,
+	.set_pauseparam_panic	= bcmgenet_set_pauseparam_panic,
 };
 
 /* Power down the unimac, based on mode. */
diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.h b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
index 5ec3979779ec..faf0d2406e9a 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.h
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
@@ -738,6 +738,7 @@ int bcmgenet_mii_config(struct net_device *dev, bool init);
 int bcmgenet_mii_probe(struct net_device *dev);
 void bcmgenet_mii_exit(struct net_device *dev);
 void bcmgenet_phy_pause_set(struct net_device *dev, bool rx, bool tx);
+void bcmgenet_set_pause_panic(struct bcmgenet_priv *priv);
 void bcmgenet_phy_power_set(struct net_device *dev, bool enable);
 void bcmgenet_mii_setup(struct net_device *dev);
 
diff --git a/drivers/net/ethernet/broadcom/genet/bcmmii.c b/drivers/net/ethernet/broadcom/genet/bcmmii.c
index 38f854b94a79..8eca6a1a8626 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmmii.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmmii.c
@@ -147,6 +147,16 @@ void bcmgenet_phy_pause_set(struct net_device *dev, bool rx, bool tx)
 	mutex_unlock(&phydev->lock);
 }
 
+void bcmgenet_set_pause_panic(struct bcmgenet_priv *priv)
+{
+	u32 reg;
+
+	/* Disable pause frame generation */
+	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
+	reg |= CMD_TX_PAUSE_IGNORE;
+	bcmgenet_umac_writel(priv, reg, UMAC_CMD);
+}
+
 void bcmgenet_phy_power_set(struct net_device *dev, bool enable)
 {
 	struct bcmgenet_priv *priv = netdev_priv(dev);
-- 
2.34.1