[PATCH net-next v7 1/5] net: add dev->bql flag to allow BQL sysfs for IFF_NO_QUEUE devices
From: hawk@kernel.org
Date: 2026-06-12 08:35:42
Also in:
linux-doc, lkml
Subsystem:
documentation, networking drivers, networking [general], the rest · Maintainers:
Jonathan Corbet, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Jesper Dangaard Brouer <hawk@kernel.org> Virtual devices with IFF_NO_QUEUE or lltx are excluded from BQL sysfs by netdev_uses_bql(), since they traditionally lack real hardware queues. However, some virtual devices like veth implement a real ptr_ring FIFO with NAPI processing and benefit from BQL to limit in-flight bytes and reduce latency. Add a per-device 'bql' bitfield boolean in the priv_flags_slow section of struct net_device. When set, it overrides the IFF_NO_QUEUE/lltx exclusion and exposes BQL sysfs entries (/sys/class/net/<dev>/queues/ tx-<n>/byte_queue_limits/). The flag is still gated on CONFIG_BQL. This allows drivers that use BQL despite being IFF_NO_QUEUE to opt in to sysfs visibility for monitoring and debugging. Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org> Tested-by: Jonas Köppeler <redacted> --- Documentation/networking/net_cachelines/net_device.rst | 1 + include/linux/netdevice.h | 2 ++ net/core/net-sysfs.c | 8 +++++++- 3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index eb2e6851c6f6..a65d48b6ecc1 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst@@ -169,6 +169,7 @@ unsigned_long:1 see_all_hwtstamp_requests unsigned_long:1 change_proto_down unsigned_long:1 netns_immutable unsigned_long:1 fcoe_mtu +unsigned_long:1 bql netdev_uses_bql(net-sysfs.c) struct list_head net_notifier_list struct macsec_ops* macsec_ops struct udp_tunnel_nic_info* udp_tunnel_nic_info
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7f4f0837c09f..f699fded20b4 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -2079,6 +2079,7 @@ enum netdev_reg_state { * @change_proto_down: device supports setting carrier via IFLA_PROTO_DOWN * @netns_immutable: interface can't change network namespaces * @fcoe_mtu: device supports maximum FCoE MTU, 2158 bytes + * @bql: device uses BQL (DQL sysfs) despite having IFF_NO_QUEUE * * @net_notifier_list: List of per-net netdev notifier block * that follow this device when it is moved
@@ -2495,6 +2496,7 @@ struct net_device { unsigned long change_proto_down:1; unsigned long netns_immutable:1; unsigned long fcoe_mtu:1; + unsigned long bql:1; struct list_head net_notifier_list;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 0e71c9ed41e8..3cb470b0f17d 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c@@ -1939,10 +1939,16 @@ static const struct kobj_type netdev_queue_ktype = { static bool netdev_uses_bql(const struct net_device *dev) { + if (!IS_ENABLED(CONFIG_BQL)) + return false; + + if (dev->bql) + return true; + if (dev->lltx || (dev->priv_flags & IFF_NO_QUEUE)) return false; - return IS_ENABLED(CONFIG_BQL); + return true; } static int netdev_queue_add_kobject(struct net_device *dev, int index)
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2.43.0