Since the driver always enables tx bounce buffer,
there are minimum values for `copybreak` and `tx_spare_buf_size`.

This patch will check and reject configurations
with values smaller than these minimums.

Closes: https://lore.kernel.org/all/20250723072900.GV2459@horms.kernel.org/
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
---
 .../ethernet/hisilicon/hns3/hns3_ethtool.c    | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c b/drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c
index d5454e126c85..a752d0e3db3a 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c
@@ -1927,6 +1927,31 @@ static int hns3_set_tx_spare_buf_size(struct net_device *netdev,
 	return ret;
 }
 
+static int hns3_check_tx_copybreak(struct net_device *netdev, u32 copybreak)
+{
+	struct hns3_nic_priv *priv = netdev_priv(netdev);
+
+	if (copybreak < priv->min_tx_copybreak) {
+		netdev_err(netdev, "tx copybreak %u should be no less than %u!\n",
+			   copybreak, priv->min_tx_copybreak);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int hns3_check_tx_spare_buf_size(struct net_device *netdev, u32 buf_size)
+{
+	struct hns3_nic_priv *priv = netdev_priv(netdev);
+
+	if (buf_size < priv->min_tx_spare_buf_size) {
+		netdev_err(netdev,
+			   "tx spare buf size %u should be no less than %u!\n",
+			   buf_size, priv->min_tx_spare_buf_size);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 static int hns3_set_tunable(struct net_device *netdev,
 			    const struct ethtool_tunable *tuna,
 			    const void *data)
@@ -1943,6 +1968,10 @@ static int hns3_set_tunable(struct net_device *netdev,
 
 	switch (tuna->id) {
 	case ETHTOOL_TX_COPYBREAK:
+		ret = hns3_check_tx_copybreak(netdev, *(u32 *)data);
+		if (ret)
+			return ret;
+
 		priv->tx_copybreak = *(u32 *)data;
 
 		for (i = 0; i < h->kinfo.num_tqps; i++)
@@ -1957,6 +1986,10 @@ static int hns3_set_tunable(struct net_device *netdev,
 
 		break;
 	case ETHTOOL_TX_COPYBREAK_BUF_SIZE:
+		ret = hns3_check_tx_spare_buf_size(netdev, *(u32 *)data);
+		if (ret)
+			return ret;
+
 		old_tx_spare_buf_size = h->kinfo.tx_spare_buf_size;
 		new_tx_spare_buf_size = *(u32 *)data;
 		netdev_info(netdev, "request to set tx spare buf size from %u to %u\n",
-- 
2.33.0