[RFC v2 03/24] net: ethtool: report max value for rx-buf-len
From: Pavel Begunkov
Date: Fri Aug 08 2025 - 10:54:38 EST
From: Jakub Kicinski <kuba@xxxxxxxxxx>
Unlike most of our APIs the rx-buf-len param does not have an associated
max value. In theory user could set this value pretty high, but in
practice most NICs have limits due to the width of the length fields
in the descriptors.
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
Documentation/netlink/specs/ethtool.yaml | 4 ++++
Documentation/networking/ethtool-netlink.rst | 1 +
drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c | 3 ++-
include/linux/ethtool.h | 2 ++
include/uapi/linux/ethtool_netlink_generated.h | 1 +
net/ethtool/rings.c | 5 +++++
6 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
index 1063d5d32fea..77627f1ec54e 100644
--- a/Documentation/netlink/specs/ethtool.yaml
+++ b/Documentation/netlink/specs/ethtool.yaml
@@ -449,6 +449,9 @@ attribute-sets:
-
name: hds-thresh-max
type: u32
+ -
+ name: rx-buf-len-max
+ type: u32
-
name: mm-stat
@@ -2046,6 +2049,7 @@ operations:
- rx-jumbo
- tx
- rx-buf-len
+ - rx-buf-len-max
- tcp-data-split
- cqe-size
- tx-push
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index cae372f719d1..05a7f6b3f945 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -902,6 +902,7 @@ Kernel response contents:
``ETHTOOL_A_RINGS_RX_JUMBO`` u32 size of RX jumbo ring
``ETHTOOL_A_RINGS_TX`` u32 size of TX ring
``ETHTOOL_A_RINGS_RX_BUF_LEN`` u32 size of buffers on the ring
+ ``ETHTOOL_A_RINGS_RX_BUF_LEN_MAX`` u32 max size of rx buffers
``ETHTOOL_A_RINGS_TCP_DATA_SPLIT`` u8 TCP header / data split
``ETHTOOL_A_RINGS_CQE_SIZE`` u32 Size of TX/RX CQE
``ETHTOOL_A_RINGS_TX_PUSH`` u8 flag of TX Push mode
diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
index 998c734ff839..1c8a7ee2e459 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
@@ -377,6 +377,7 @@ static void otx2_get_ringparam(struct net_device *netdev,
ring->tx_max_pending = Q_COUNT(Q_SIZE_MAX);
ring->tx_pending = qs->sqe_cnt ? qs->sqe_cnt : Q_COUNT(Q_SIZE_4K);
kernel_ring->rx_buf_len = pfvf->hw.rbuf_len;
+ kernel_ring->rx_buf_len_max = 32768;
kernel_ring->cqe_size = pfvf->hw.xqe_size;
}
@@ -399,7 +400,7 @@ static int otx2_set_ringparam(struct net_device *netdev,
/* Hardware supports max size of 32k for a receive buffer
* and 1536 is typical ethernet frame size.
*/
- if (rx_buf_len && (rx_buf_len < 1536 || rx_buf_len > 32768)) {
+ if (rx_buf_len && (rx_buf_len < 1536)) {
netdev_err(netdev,
"Receive buffer range is 1536 - 32768");
return -EINVAL;
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index de5bd76a400c..9267bac16195 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -77,6 +77,7 @@ enum {
/**
* struct kernel_ethtool_ringparam - RX/TX ring configuration
* @rx_buf_len: Current length of buffers on the rx ring.
+ * @rx_buf_len_max: Max length of buffers on the rx ring.
* @tcp_data_split: Scatter packet headers and data to separate buffers
* @tx_push: The flag of tx push mode
* @rx_push: The flag of rx push mode
@@ -89,6 +90,7 @@ enum {
*/
struct kernel_ethtool_ringparam {
u32 rx_buf_len;
+ u32 rx_buf_len_max;
u8 tcp_data_split;
u8 tx_push;
u8 rx_push;
diff --git a/include/uapi/linux/ethtool_netlink_generated.h b/include/uapi/linux/ethtool_netlink_generated.h
index e3b8813465d7..8b293d3499f1 100644
--- a/include/uapi/linux/ethtool_netlink_generated.h
+++ b/include/uapi/linux/ethtool_netlink_generated.h
@@ -192,6 +192,7 @@ enum {
ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN_MAX,
ETHTOOL_A_RINGS_HDS_THRESH,
ETHTOOL_A_RINGS_HDS_THRESH_MAX,
+ ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
__ETHTOOL_A_RINGS_CNT,
ETHTOOL_A_RINGS_MAX = (__ETHTOOL_A_RINGS_CNT - 1)
diff --git a/net/ethtool/rings.c b/net/ethtool/rings.c
index aeedd5ec6b8c..5e872ceab5dd 100644
--- a/net/ethtool/rings.c
+++ b/net/ethtool/rings.c
@@ -105,6 +105,9 @@ static int rings_fill_reply(struct sk_buff *skb,
ringparam->tx_pending))) ||
(kr->rx_buf_len &&
(nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN, kr->rx_buf_len))) ||
+ (kr->rx_buf_len_max &&
+ (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
+ kr->rx_buf_len_max))) ||
(kr->tcp_data_split &&
(nla_put_u8(skb, ETHTOOL_A_RINGS_TCP_DATA_SPLIT,
kr->tcp_data_split))) ||
@@ -281,6 +284,8 @@ ethnl_set_rings(struct ethnl_req_info *req_info, struct genl_info *info)
err_attr = tb[ETHTOOL_A_RINGS_TX];
else if (kernel_ringparam.hds_thresh > kernel_ringparam.hds_thresh_max)
err_attr = tb[ETHTOOL_A_RINGS_HDS_THRESH];
+ else if (kernel_ringparam.rx_buf_len > kernel_ringparam.rx_buf_len_max)
+ err_attr = tb[ETHTOOL_A_RINGS_RX_BUF_LEN];
else
err_attr = NULL;
if (err_attr) {
--
2.49.0