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Mon, 13 Oct 2025 07:53:56 -0700 (PDT) From: Pavel Begunkov To: netdev@vger.kernel.org Cc: Andrew Lunn , Jakub Kicinski , davem@davemloft.net, Eric Dumazet , Paolo Abeni , Simon Horman , Donald Hunter , Michael Chan , Pavan Chebbi , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Joshua Washington , Harshitha Ramamurthy , Jian Shen , Salil Mehta , Jijie Shao , Sunil Goutham , Geetha sowjanya , Subbaraya Sundeep , hariprasad , Bharat Bhushan , Saeed Mahameed , Tariq Toukan , Mark Bloch , Leon Romanovsky , Alexander Duyck , kernel-team@meta.com, Ilias Apalodimas , Joe Damato , David Wei , Willem de Bruijn , Mina Almasry , Pavel Begunkov , Breno Leitao , Dragos Tatulea , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-rdma@vger.kernel.org, Jonathan Corbet Subject: [PATCH net-next v4 19/24] netdev: add support for setting rx-buf-len per queue Date: Mon, 13 Oct 2025 15:54:21 +0100 Message-ID: X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jakub Kicinski Zero-copy APIs increase the cost of buffer management. They also extend this cost to user space applications which may be used to dealing with much larger buffers. Allow setting rx-buf-len per queue, devices with HW-GRO support can commonly fill buffers up to 32k (or rather 64k - 1 but that's not a power of 2..) The implementation adds a new option to the netdev netlink, rather than ethtool. The NIC-wide setting lives in ethtool ringparams so one could argue that we should be extending the ethtool API. OTOH netdev API is where we already have queue-get, and it's how zero-copy applications bind memory providers. Signed-off-by: Jakub Kicinski Signed-off-by: Pavel Begunkov --- Documentation/netlink/specs/netdev.yaml | 15 ++++ include/net/netdev_queues.h | 5 ++ include/net/netlink.h | 19 +++++ include/uapi/linux/netdev.h | 2 + net/core/netdev-genl-gen.c | 15 ++++ net/core/netdev-genl-gen.h | 1 + net/core/netdev-genl.c | 92 +++++++++++++++++++++++++ net/core/netdev_config.c | 16 +++++ tools/include/uapi/linux/netdev.h | 2 + 9 files changed, 167 insertions(+) diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlin= k/specs/netdev.yaml index e00d3fa1c152..fabae13f45e8 100644 --- a/Documentation/netlink/specs/netdev.yaml +++ b/Documentation/netlink/specs/netdev.yaml @@ -338,6 +338,10 @@ attribute-sets: doc: XSK information for this queue, if any. type: nest nested-attributes: xsk-info + - + name: rx-buf-len + doc: Per-queue configuration of ETHTOOL_A_RINGS_RX_BUF_LEN. + type: u32 - name: qstats doc: | @@ -771,6 +775,17 @@ operations: reply: attributes: - id + - + name: queue-set + doc: Set per-queue configurable options. + attribute-set: queue + do: + request: + attributes: + - ifindex + - type + - id + - rx-buf-len =20 kernel-family: headers: ["net/netdev_netlink.h"] diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h index 532f60ee1a66..4b59ca9d5a4b 100644 --- a/include/net/netdev_queues.h +++ b/include/net/netdev_queues.h @@ -39,6 +39,7 @@ struct netdev_config { =20 /* Same semantics as fields in struct netdev_config */ struct netdev_queue_config { + u32 rx_buf_len; }; =20 /* See the netdev.yaml spec for definition of each statistic */ @@ -141,6 +142,8 @@ void netdev_stat_queue_sum(struct net_device *netdev, /** * struct netdev_queue_mgmt_ops - netdev ops for queue management * + * @supported_ring_params: ring params supported per queue (ETHTOOL_RING_U= SE_*). + * * @ndo_queue_mem_size: Size of the struct that describes a queue's memory. * * @ndo_queue_cfg_defaults: (Optional) Populate queue config struct with @@ -174,6 +177,8 @@ void netdev_stat_queue_sum(struct net_device *netdev, * be called for an interface which is open. */ struct netdev_queue_mgmt_ops { + u32 supported_ring_params; + size_t ndo_queue_mem_size; void (*ndo_queue_cfg_defaults)(struct net_device *dev, int idx, diff --git a/include/net/netlink.h b/include/net/netlink.h index 1a8356ca4b78..29989ad81ddd 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -2200,6 +2200,25 @@ static inline struct nla_bitfield32 nla_get_bitfield= 32(const struct nlattr *nla) return tmp; } =20 +/** + * nla_update_u32() - update u32 value from NLA_U32 attribute + * @dst: value to update + * @attr: netlink attribute with new value or null + * + * Copy the u32 value from NLA_U32 netlink attribute @attr into variable + * pointed to by @dst; do nothing if @attr is null. + * + * Return: true if this function changed the value of @dst, otherwise fals= e. + */ +static inline bool nla_update_u32(u32 *dst, const struct nlattr *attr) +{ + u32 old_val =3D *dst; + + if (attr) + *dst =3D nla_get_u32(attr); + return *dst !=3D old_val; +} + /** * nla_memdup - duplicate attribute memory (kmemdup) * @src: netlink attribute to duplicate from diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h index 48eb49aa03d4..820f89b67a72 100644 --- a/include/uapi/linux/netdev.h +++ b/include/uapi/linux/netdev.h @@ -158,6 +158,7 @@ enum { NETDEV_A_QUEUE_DMABUF, NETDEV_A_QUEUE_IO_URING, NETDEV_A_QUEUE_XSK, + NETDEV_A_QUEUE_RX_BUF_LEN, =20 __NETDEV_A_QUEUE_MAX, NETDEV_A_QUEUE_MAX =3D (__NETDEV_A_QUEUE_MAX - 1) @@ -226,6 +227,7 @@ enum { NETDEV_CMD_BIND_RX, NETDEV_CMD_NAPI_SET, NETDEV_CMD_BIND_TX, + NETDEV_CMD_QUEUE_SET, =20 __NETDEV_CMD_MAX, NETDEV_CMD_MAX =3D (__NETDEV_CMD_MAX - 1) diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c index e9a2a6f26cb7..d053306a3af8 100644 --- a/net/core/netdev-genl-gen.c +++ b/net/core/netdev-genl-gen.c @@ -106,6 +106,14 @@ static const struct nla_policy netdev_bind_tx_nl_polic= y[NETDEV_A_DMABUF_FD + 1] [NETDEV_A_DMABUF_FD] =3D { .type =3D NLA_U32, }, }; =20 +/* NETDEV_CMD_QUEUE_SET - do */ +static const struct nla_policy netdev_queue_set_nl_policy[NETDEV_A_QUEUE_R= X_BUF_LEN + 1] =3D { + [NETDEV_A_QUEUE_IFINDEX] =3D NLA_POLICY_MIN(NLA_U32, 1), + [NETDEV_A_QUEUE_TYPE] =3D NLA_POLICY_MAX(NLA_U32, 1), + [NETDEV_A_QUEUE_ID] =3D { .type =3D NLA_U32, }, + [NETDEV_A_QUEUE_RX_BUF_LEN] =3D { .type =3D NLA_U32, }, +}; + /* Ops table for netdev */ static const struct genl_split_ops netdev_nl_ops[] =3D { { @@ -204,6 +212,13 @@ static const struct genl_split_ops netdev_nl_ops[] =3D= { .maxattr =3D NETDEV_A_DMABUF_FD, .flags =3D GENL_CMD_CAP_DO, }, + { + .cmd =3D NETDEV_CMD_QUEUE_SET, + .doit =3D netdev_nl_queue_set_doit, + .policy =3D netdev_queue_set_nl_policy, + .maxattr =3D NETDEV_A_QUEUE_RX_BUF_LEN, + .flags =3D GENL_CMD_CAP_DO, + }, }; =20 static const struct genl_multicast_group netdev_nl_mcgrps[] =3D { diff --git a/net/core/netdev-genl-gen.h b/net/core/netdev-genl-gen.h index cf3fad74511f..b7f5e5d9fca9 100644 --- a/net/core/netdev-genl-gen.h +++ b/net/core/netdev-genl-gen.h @@ -35,6 +35,7 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb, int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info); int netdev_nl_napi_set_doit(struct sk_buff *skb, struct genl_info *info); int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info); +int netdev_nl_queue_set_doit(struct sk_buff *skb, struct genl_info *info); =20 enum { NETDEV_NLGRP_MGMT, diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c index 470fabbeacd9..61529b600c87 100644 --- a/net/core/netdev-genl.c +++ b/net/core/netdev-genl.c @@ -386,6 +386,30 @@ static int nla_put_napi_id(struct sk_buff *skb, const = struct napi_struct *napi) return 0; } =20 +static int +netdev_nl_queue_fill_cfg(struct sk_buff *rsp, struct net_device *netdev, + u32 q_idx, u32 q_type) +{ + struct netdev_queue_config *qcfg; + + if (!netdev_need_ops_lock(netdev)) + return 0; + + qcfg =3D &netdev->cfg->qcfg[q_idx]; + switch (q_type) { + case NETDEV_QUEUE_TYPE_RX: + if (qcfg->rx_buf_len && + nla_put_u32(rsp, NETDEV_A_QUEUE_RX_BUF_LEN, + qcfg->rx_buf_len)) + return -EMSGSIZE; + break; + default: + break; + } + + return 0; +} + static int netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev, u32 q_idx, u32 q_type, const struct genl_info *info) @@ -433,6 +457,9 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct ne= t_device *netdev, break; } =20 + if (netdev_nl_queue_fill_cfg(rsp, netdev, q_idx, q_type)) + goto nla_put_failure; + genlmsg_end(rsp, hdr); =20 return 0; @@ -572,6 +599,71 @@ int netdev_nl_queue_get_dumpit(struct sk_buff *skb, st= ruct netlink_callback *cb) return err; } =20 +int netdev_nl_queue_set_doit(struct sk_buff *skb, struct genl_info *info) +{ + struct nlattr * const *tb =3D info->attrs; + struct netdev_queue_config *qcfg; + u32 q_id, q_type, ifindex; + struct net_device *netdev; + bool mod; + int ret; + + if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_ID) || + GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_TYPE) || + GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_IFINDEX)) + return -EINVAL; + + q_id =3D nla_get_u32(tb[NETDEV_A_QUEUE_ID]); + q_type =3D nla_get_u32(tb[NETDEV_A_QUEUE_TYPE]); + ifindex =3D nla_get_u32(tb[NETDEV_A_QUEUE_IFINDEX]); + + if (q_type !=3D NETDEV_QUEUE_TYPE_RX) { + /* Only Rx params exist right now */ + NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_TYPE]); + return -EINVAL; + } + + ret =3D 0; + netdev =3D netdev_get_by_index_lock(genl_info_net(info), ifindex); + if (!netdev || !netif_device_present(netdev)) + ret =3D -ENODEV; + else if (!netdev->queue_mgmt_ops) + ret =3D -EOPNOTSUPP; + if (ret) { + NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_IFINDEX]); + goto exit_unlock; + } + + ret =3D netdev_nl_queue_validate(netdev, q_id, q_type); + if (ret) { + NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_ID]); + goto exit_unlock; + } + + ret =3D netdev_reconfig_start(netdev); + if (ret) + goto exit_unlock; + + qcfg =3D &netdev->cfg_pending->qcfg[q_id]; + mod =3D nla_update_u32(&qcfg->rx_buf_len, tb[NETDEV_A_QUEUE_RX_BUF_LEN]); + if (!mod) + goto exit_free_cfg; + + ret =3D netdev_rx_queue_restart(netdev, q_id, info->extack); + if (ret) + goto exit_free_cfg; + + swap(netdev->cfg, netdev->cfg_pending); + +exit_free_cfg: + __netdev_free_config(netdev->cfg_pending); + netdev->cfg_pending =3D netdev->cfg; +exit_unlock: + if (netdev) + netdev_unlock(netdev); + return ret; +} + #define NETDEV_STAT_NOT_SET (~0ULL) =20 static void netdev_nl_stats_add(void *_sum, const void *_add, size_t size) diff --git a/net/core/netdev_config.c b/net/core/netdev_config.c index fc700b77e4eb..ede02b77470e 100644 --- a/net/core/netdev_config.c +++ b/net/core/netdev_config.c @@ -67,11 +67,27 @@ int netdev_reconfig_start(struct net_device *dev) void __netdev_queue_config(struct net_device *dev, int rxq, struct netdev_queue_config *qcfg, bool pending) { + const struct netdev_config *cfg; + + cfg =3D pending ? dev->cfg_pending : dev->cfg; + memset(qcfg, 0, sizeof(*qcfg)); =20 /* Get defaults from the driver, in case user config not set */ if (dev->queue_mgmt_ops->ndo_queue_cfg_defaults) dev->queue_mgmt_ops->ndo_queue_cfg_defaults(dev, rxq, qcfg); + + /* Set config based on device-level settings */ + if (cfg->rx_buf_len) + qcfg->rx_buf_len =3D cfg->rx_buf_len; + + /* Set config dedicated to this queue */ + if (rxq >=3D 0) { + const struct netdev_queue_config *user_cfg =3D &cfg->qcfg[rxq]; + + if (user_cfg->rx_buf_len) + qcfg->rx_buf_len =3D user_cfg->rx_buf_len; + } } =20 /** diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/n= etdev.h index 48eb49aa03d4..820f89b67a72 100644 --- a/tools/include/uapi/linux/netdev.h +++ b/tools/include/uapi/linux/netdev.h @@ -158,6 +158,7 @@ enum { NETDEV_A_QUEUE_DMABUF, NETDEV_A_QUEUE_IO_URING, NETDEV_A_QUEUE_XSK, + NETDEV_A_QUEUE_RX_BUF_LEN, =20 __NETDEV_A_QUEUE_MAX, NETDEV_A_QUEUE_MAX =3D (__NETDEV_A_QUEUE_MAX - 1) @@ -226,6 +227,7 @@ enum { NETDEV_CMD_BIND_RX, NETDEV_CMD_NAPI_SET, NETDEV_CMD_BIND_TX, + NETDEV_CMD_QUEUE_SET, =20 __NETDEV_CMD_MAX, NETDEV_CMD_MAX =3D (__NETDEV_CMD_MAX - 1) --=20 2.49.0