[PATCH V2 net 0/3] There are some bugfix for hibmcge ethernet driver

[PATCH V2 net 0/3] There are some bugfix for hibmcge ethernet driver

[Jijie Shao]

This patch set is intended to fix several issues for hibmcge driver:
1. Holding the rtnl_lock in pci_error_handlers->reset_prepare()
   may lead to a deadlock issue.
2. A division by zero issue caused by debugfs when the port is down.
3. A probabilistic false positive issue with np_link_fail.

---
ChangeLog:
v1 -> v2:
  - Fix a concurrency issue for patch1, suggested by Simon Horman
  v1: https://lore.kernel.org/all/20250731134749.4090041-1-shaojijie@huawei.com/
---

Jijie Shao (3):
  net: hibmcge: fix rtnl deadlock issue
  net: hibmcge: fix the division by zero issue
  net: hibmcge: fix the np_link_fail error reporting issue

 drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c  | 14 +++++---------
 drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c   | 15 +++++++++++++--
 drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h |  3 +++
 3 files changed, 21 insertions(+), 11 deletions(-)

-- 
2.33.0

[PATCH V2 net 1/3] net: hibmcge: fix rtnl deadlock issue

[Jijie Shao]

Currently, the hibmcge netdev acquires the rtnl_lock in
pci_error_handlers.reset_prepare() and releases it in
pci_error_handlers.reset_done().

However, in the PCI framework:
pci_reset_bus - __pci_reset_slot - pci_slot_save_and_disable_locked -
 pci_dev_save_and_disable - err_handler->reset_prepare(dev);

In pci_slot_save_and_disable_locked():
	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
		if (!dev->slot || dev->slot!= slot)
			continue;
		pci_dev_save_and_disable(dev);
		if (dev->subordinate)
			pci_bus_save_and_disable_locked(dev->subordinate);
	}

This will iterate through all devices under the current bus and execute
err_handler->reset_prepare(), causing two devices of the hibmcge driver
to sequentially request the rtnl_lock, leading to a deadlock.

Since the driver now executes netif_device_detach()
before the reset process, it will not concurrently with
other netdev APIs, so there is no need to hold the rtnl_lock now.

Therefore, this patch removes the rtnl_lock during the reset process and
adjusts the position of HBG_NIC_STATE_RESETTING to ensure
that multiple resets are not executed concurrently.

Fixes: 3f5a61f6d504f ("net: hibmcge: Add reset supported in this module")
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
---
ChangeLog:
v1 -> v2:
  - Fix a concurrency issue, suggested by Simon Horman
  v1: https://lore.kernel.org/all/20250731134749.4090041-1-shaojijie@huawei.com/
---
 drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c b/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c
index 503cfbfb4a8a..83cf75bf7a17 100644
--- a/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c
+++ b/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c
@@ -53,9 +53,11 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type)
 {
 	int ret;
 
-	ASSERT_RTNL();
+	if (test_and_set_bit(HBG_NIC_STATE_RESETTING, &priv->state))
+		return -EBUSY;
 
 	if (netif_running(priv->netdev)) {
+		clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 		dev_warn(&priv->pdev->dev,
 			 "failed to reset because port is up\n");
 		return -EBUSY;
@@ -64,7 +66,6 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type)
 	netif_device_detach(priv->netdev);
 
 	priv->reset_type = type;
-	set_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 	clear_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state);
 	ret = hbg_hw_event_notify(priv, HBG_HW_EVENT_RESET);
 	if (ret) {
@@ -84,29 +85,26 @@ static int hbg_reset_done(struct hbg_priv *priv, enum hbg_reset_type type)
 	    type != priv->reset_type)
 		return 0;
 
-	ASSERT_RTNL();
-
-	clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 	ret = hbg_rebuild(priv);
 	if (ret) {
 		priv->stats.reset_fail_cnt++;
 		set_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state);
+		clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 		dev_err(&priv->pdev->dev, "failed to rebuild after reset\n");
 		return ret;
 	}
 
 	netif_device_attach(priv->netdev);
+	clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 
 	dev_info(&priv->pdev->dev, "reset done\n");
 	return ret;
 }
 
-/* must be protected by rtnl lock */
 int hbg_reset(struct hbg_priv *priv)
 {
 	int ret;
 
-	ASSERT_RTNL();
 	ret = hbg_reset_prepare(priv, HBG_RESET_TYPE_FUNCTION);
 	if (ret)
 		return ret;
@@ -171,7 +169,6 @@ static void hbg_pci_err_reset_prepare(struct pci_dev *pdev)
 	struct net_device *netdev = pci_get_drvdata(pdev);
 	struct hbg_priv *priv = netdev_priv(netdev);
 
-	rtnl_lock();
 	hbg_reset_prepare(priv, HBG_RESET_TYPE_FLR);
 }
 
@@ -181,7 +178,6 @@ static void hbg_pci_err_reset_done(struct pci_dev *pdev)
 	struct hbg_priv *priv = netdev_priv(netdev);
 
 	hbg_reset_done(priv, HBG_RESET_TYPE_FLR);
-	rtnl_unlock();
 }
 
 static const struct pci_error_handlers hbg_pci_err_handler = {
-- 
2.33.0

[PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue

[Jijie Shao]

When the network port is down, the queue is released, and ring->len is 0.
In debugfs, hbg_get_queue_used_num() will be called,
which may lead to a division by zero issue.

This patch adds a check, if ring->len is 0,
hbg_get_queue_used_num() directly returns 0.

Fixes: 40735e7543f9 ("net: hibmcge: Implement .ndo_start_xmit function")
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
---
 drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h b/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
index 2883a5899ae2..2aecc73f3d49 100644
--- a/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
+++ b/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
@@ -29,6 +29,9 @@ static inline bool hbg_fifo_is_full(struct hbg_priv *priv, enum hbg_dir dir)
 
 static inline u32 hbg_get_queue_used_num(struct hbg_ring *ring)
 {
+	if (!ring->len)
+		return 0;
+
 	return (ring->ntu + ring->len - ring->ntc) % ring->len;
 }
 
-- 
2.33.0

[PATCH V2 net 3/3] net: hibmcge: fix the np_link_fail error reporting issue

[Jijie Shao]

Currently, after modifying device port mode, the np_link_ok state
is immediately checked. At this point, the device may not yet ready,
leading to the querying of an intermediate state.

This patch will poll to check if np_link is ok after
modifying device port mode, and only report np_link_fail upon timeout.

Fixes: e0306637e85d ("net: hibmcge: Add support for mac link exception handling feature")
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
---
 drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c b/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c
index 8cca8316ba40..d0aa0661ecd4 100644
--- a/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c
+++ b/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c
@@ -12,6 +12,8 @@
 
 #define HBG_HW_EVENT_WAIT_TIMEOUT_US	(2 * 1000 * 1000)
 #define HBG_HW_EVENT_WAIT_INTERVAL_US	(10 * 1000)
+#define HBG_MAC_LINK_WAIT_TIMEOUT_US	(500 * 1000)
+#define HBG_MAC_LINK_WAIT_INTERVAL_US	(5 * 1000)
 /* little endian or big endian.
  * ctrl means packet description, data means skb packet data
  */
@@ -228,6 +230,9 @@ void hbg_hw_fill_buffer(struct hbg_priv *priv, u32 buffer_dma_addr)
 
 void hbg_hw_adjust_link(struct hbg_priv *priv, u32 speed, u32 duplex)
 {
+	u32 link_status;
+	int ret;
+
 	hbg_hw_mac_enable(priv, HBG_STATUS_DISABLE);
 
 	hbg_reg_write_field(priv, HBG_REG_PORT_MODE_ADDR,
@@ -239,8 +244,14 @@ void hbg_hw_adjust_link(struct hbg_priv *priv, u32 speed, u32 duplex)
 
 	hbg_hw_mac_enable(priv, HBG_STATUS_ENABLE);
 
-	if (!hbg_reg_read_field(priv, HBG_REG_AN_NEG_STATE_ADDR,
-				HBG_REG_AN_NEG_STATE_NP_LINK_OK_B))
+	/* wait MAC link up */
+	ret = readl_poll_timeout(priv->io_base + HBG_REG_AN_NEG_STATE_ADDR,
+				 link_status,
+				 FIELD_GET(HBG_REG_AN_NEG_STATE_NP_LINK_OK_B,
+					   link_status),
+				 HBG_MAC_LINK_WAIT_INTERVAL_US,
+				 HBG_MAC_LINK_WAIT_TIMEOUT_US);
+	if (ret)
 		hbg_np_link_fail_task_schedule(priv);
 }
 
-- 
2.33.0

Re: [PATCH V2 net 1/3] net: hibmcge: fix rtnl deadlock issue

[Simon Horman]

On Sat, Aug 02, 2025 at 08:32:24PM +0800, Jijie Shao wrote:
> Currently, the hibmcge netdev acquires the rtnl_lock in
> pci_error_handlers.reset_prepare() and releases it in
> pci_error_handlers.reset_done().
> 
> However, in the PCI framework:
> pci_reset_bus - __pci_reset_slot - pci_slot_save_and_disable_locked -
>  pci_dev_save_and_disable - err_handler->reset_prepare(dev);
> 
> In pci_slot_save_and_disable_locked():
> 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
> 		if (!dev->slot || dev->slot!= slot)
> 			continue;
> 		pci_dev_save_and_disable(dev);
> 		if (dev->subordinate)
> 			pci_bus_save_and_disable_locked(dev->subordinate);
> 	}
> 
> This will iterate through all devices under the current bus and execute
> err_handler->reset_prepare(), causing two devices of the hibmcge driver
> to sequentially request the rtnl_lock, leading to a deadlock.
> 
> Since the driver now executes netif_device_detach()
> before the reset process, it will not concurrently with
> other netdev APIs, so there is no need to hold the rtnl_lock now.
> 
> Therefore, this patch removes the rtnl_lock during the reset process and
> adjusts the position of HBG_NIC_STATE_RESETTING to ensure
> that multiple resets are not executed concurrently.
> 
> Fixes: 3f5a61f6d504f ("net: hibmcge: Add reset supported in this module")
> Signed-off-by: Jijie Shao <shaojijie@huawei.com>
> ---
> ChangeLog:
> v1 -> v2:
>   - Fix a concurrency issue, suggested by Simon Horman
>   v1: https://lore.kernel.org/all/20250731134749.4090041-1-shaojijie@huawei.com/

Thanks for the update.

This version looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue

[Jakub Kicinski]

On Sat, 2 Aug 2025 20:32:25 +0800 Jijie Shao wrote:
>  static inline u32 hbg_get_queue_used_num(struct hbg_ring *ring)
>  {
> +	if (!ring->len)
> +		return 0;
> +
>  	return (ring->ntu + ring->len - ring->ntc) % ring->len;

This should probably be a READ_ONCE() to a temporary variable.
There is no locking in debugfs, AFAICT, the value may change
between the test and the division / modulo.
-- 
pw-bot: cr

Re: [PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue

[Jijie Shao]

on 2025/8/6 9:14, Jakub Kicinski wrote:
> On Sat, 2 Aug 2025 20:32:25 +0800 Jijie Shao wrote:
>>   static inline u32 hbg_get_queue_used_num(struct hbg_ring *ring)
>>   {
>> +	if (!ring->len)
>> +		return 0;
>> +
>>   	return (ring->ntu + ring->len - ring->ntc) % ring->len;
> This should probably be a READ_ONCE() to a temporary variable.
> There is no locking in debugfs, AFAICT, the value may change
> between the test and the division / modulo.

Yes, there is indeed a very short time window.
I will add READ_ONCE() to ring->len and read it only once.

Thanks
Jijie Shao