netdev - [PATCH net-next v2 04/15] net, ethtool: Disallow peered real rxqs to be resized

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Message-ID: <20251015140140.62273-5-daniel@iogearbox.net>
Date: Wed, 15 Oct 2025 16:01:29 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: netdev@...r.kernel.org
Cc: bpf@...r.kernel.org,
	kuba@...nel.org,
	davem@...emloft.net,
	razor@...ckwall.org,
	pabeni@...hat.com,
	willemb@...gle.com,
	sdf@...ichev.me,
	john.fastabend@...il.com,
	martin.lau@...nel.org,
	jordan@...fe.io,
	maciej.fijalkowski@...el.com,
	magnus.karlsson@...el.com,
	dw@...idwei.uk,
	toke@...hat.com,
	yangzhenze@...edance.com,
	wangdongdong.6@...edance.com
Subject: [PATCH net-next v2 04/15] net, ethtool: Disallow peered real rxqs to be resized

Similar to AF_XDP, do not allow queues in a physical netdev to be
resized by ethtool -L when they are peered.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Co-developed-by: David Wei <dw@...idwei.uk>
Signed-off-by: David Wei <dw@...idwei.uk>
---
 include/linux/ethtool.h |  1 +
 net/ethtool/channels.c  | 12 ++++++------
 net/ethtool/common.c    | 10 +++++++++-
 net/ethtool/ioctl.c     |  4 ++--
 4 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index c2d8b4ec62eb..151fc920234d 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -1481,4 +1481,5 @@ struct ethtool_forced_speed_map {
 
 void
 ethtool_forced_speed_maps_init(struct ethtool_forced_speed_map *maps, u32 size);
+bool ethtool_channel_busy(struct net_device *dev, u32 channel);
 #endif /* _LINUX_ETHTOOL_H */
diff --git a/net/ethtool/channels.c b/net/ethtool/channels.c
index ca4f80282448..b3de8064275c 100644
--- a/net/ethtool/channels.c
+++ b/net/ethtool/channels.c
@@ -1,7 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
-#include <net/xdp_sock_drv.h>
-
 #include "netlink.h"
 #include "common.h"
 
@@ -169,14 +167,16 @@ ethnl_set_channels(struct ethnl_req_info *req_info, struct genl_info *info)
 	if (ret)
 		return ret;
 
-	/* Disabling channels, query zero-copy AF_XDP sockets */
+	/* ensure channels are not busy at the moment */
 	from_channel = channels.combined_count +
 		       min(channels.rx_count, channels.tx_count);
-	for (i = from_channel; i < old_total; i++)
-		if (xsk_get_pool_from_qid(dev, i)) {
-			GENL_SET_ERR_MSG(info, "requested channel counts are too low for existing zerocopy AF_XDP sockets");
+	for (i = from_channel; i < old_total; i++) {
+		if (ethtool_channel_busy(dev, i)) {
+			GENL_SET_ERR_MSG(info,
+					 "requested channel counts are too low due to busy queues (AF_XDP or queue peering)");
 			return -EINVAL;
 		}
+	}
 
 	ret = dev->ethtool_ops->set_channels(dev, &channels);
 	return ret < 0 ? ret : 1;
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 55223ebc2a7e..a67382c2208b 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -6,13 +6,15 @@
 #include <linux/rtnetlink.h>
 #include <linux/ptp_clock_kernel.h>
 #include <linux/phy_link_topology.h>
+
 #include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
+#include <net/xdp_sock_drv.h>
 
 #include "netlink.h"
 #include "common.h"
 #include "../core/dev.h"
 
-
 const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_SG_BIT] =               "tx-scatter-gather",
 	[NETIF_F_IP_CSUM_BIT] =          "tx-checksum-ipv4",
@@ -1101,6 +1103,12 @@ EXPORT_SYMBOL(ethtool_get_ts_info_by_layer);
 
 const struct ethtool_phy_ops *ethtool_phy_ops;
 
+bool ethtool_channel_busy(struct net_device *dev, u32 channel)
+{
+	return netdev_rx_queue_peered(dev, channel) ||
+	       xsk_get_pool_from_qid(dev, channel);
+}
+
 void ethtool_set_ethtool_phy_ops(const struct ethtool_phy_ops *ops)
 {
 	ASSERT_RTNL();
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index fa83ddade4f8..9ed87a18e48a 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2282,12 +2282,12 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 	if (ret)
 		return ret;
 
-	/* Disabling channels, query zero-copy AF_XDP sockets */
+	/* Disabling channels, query busy queues (AF_XDP, queue peering) */
 	from_channel = channels.combined_count +
 		min(channels.rx_count, channels.tx_count);
 	to_channel = curr.combined_count + max(curr.rx_count, curr.tx_count);
 	for (i = from_channel; i < to_channel; i++)
-		if (xsk_get_pool_from_qid(dev, i))
+		if (ethtool_channel_busy(dev, i))
 			return -EINVAL;
 
 	ret = dev->ethtool_ops->set_channels(dev, &channels);
-- 
2.43.0