[PATCH net-next v3 2/2] net/mlx5: implement swp_l4_csum_mode via devlink params

Daniel Zahka
2025-11-07T20:43:53Z

swp_l4_csum_mode controls how L4 transmit checksums are computed when
using Software Parser (SWP) hints for header locations.

Supported values:
1. device_default: use device default setting.
2. full_csum: calculate L4 checksum with the pseudo-header.
3. l4_only: calculate L4 checksum without the pseudo-header. Only
available when swp_l4_csum_mode_l4_only is set in
mlx5_ifc_nv_sw_offload_cap_bits.

The l4_only setting is a dependency for PSP initialization in
mlx5e_psp_init().

Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
---

Notes:
v2:
- use extack in mlx5_nv_param_devlink_swp_l4_csum_mode_get()
- fix indentation issue in mlx5.rst entry

Documentation/networking/devlink/mlx5.rst | 9 +
.../net/ethernet/mellanox/mlx5/core/devlink.h | 3 +-
.../mellanox/mlx5/core/lib/nv_param.c | 161 ++++++++++++++++++
3 files changed, 172 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/devlink/mlx5.rst b/Documentation/networking/devlink/mlx5.rst
index 0e5f9c76e514..675b5a1ec625 100644
--- a/Documentation/networking/devlink/mlx5.rst
+++ b/Documentation/networking/devlink/mlx5.rst
@@ -218,6 +218,15 @@ parameters.
* ``balanced`` : Merges fewer CQEs, resulting in a moderate compression ratio but maintaining a balance between bandwidth savings and performance
* ``aggressive`` : Merges more CQEs into a single entry, achieving a higher compression rate and maximizing performance, particularly under high traffic loads

+ * - ``swp_l4_csum_mode``
+ - string
+ - permanent
+ - Configure how the L4 checksum is calculated by the device when using
+ Software Parser (SWP) hints for header locations.
+ * ``device_default`` : Use the device's default checksum calculation mode
+ * ``full_csum`` : Calculate full checksum including the pseudo-header
+ * ``l4_only`` : Calculate L4-only checksum, excluding the pseudo-header
+
The ``mlx5`` driver supports reloading via ``DEVLINK_CMD_RELOAD``

Info versions
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/devlink.h b/drivers/net/ethernet/mellanox/mlx5/core/devlink.h
index c9555119a661..43b9bf8829cf 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/devlink.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/devlink.h
@@ -26,7 +26,8 @@ enum mlx5_devlink_param_id {
MLX5_DEVLINK_PARAM_ID_PCIE_CONG_IN_HIGH,
MLX5_DEVLINK_PARAM_ID_PCIE_CONG_OUT_LOW,
MLX5_DEVLINK_PARAM_ID_PCIE_CONG_OUT_HIGH,
- MLX5_DEVLINK_PARAM_ID_CQE_COMPRESSION_TYPE
+ MLX5_DEVLINK_PARAM_ID_CQE_COMPRESSION_TYPE,
+ MLX5_DEVLINK_PARAM_ID_SWP_L4_CSUM_MODE,
};

struct mlx5_trap_ctx {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/nv_param.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/nv_param.c
index 3d2195338d39..3dc5b899a5fb 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/nv_param.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/nv_param.c
@@ -8,6 +8,8 @@ enum {
MLX5_CLASS_0_CTRL_ID_NV_GLOBAL_PCI_CONF = 0x80,
MLX5_CLASS_0_CTRL_ID_NV_GLOBAL_PCI_CAP = 0x81,
MLX5_CLASS_0_CTRL_ID_NV_SW_OFFLOAD_CONFIG = 0x10a,
+ MLX5_CLASS_0_CTRL_ID_NV_SW_OFFLOAD_CAP = 0x10b,
+ MLX5_CLASS_0_CTRL_ID_NV_SW_ACCELERATE_CONF = 0x11d,

MLX5_CLASS_3_CTRL_ID_NV_PF_PCI_CONF = 0x80,
};
@@ -123,6 +125,17 @@ struct mlx5_ifc_nv_sw_offload_conf_bits {
u8 lro_log_timeout0[0x4];
};

+struct mlx5_ifc_nv_sw_offload_cap_bits {
+ u8 reserved_at_0[0x19];
+ u8 swp_l4_csum_mode_l4_only[0x1];
+ u8 reserved_at_1a[0x6];
+};
+
+struct mlx5_ifc_nv_sw_accelerate_conf_bits {
+ u8 swp_l4_csum_mode[0x2];
+ u8 reserved_at_2[0x3e];
+};
+
#define MNVDA_HDR_SZ \
(MLX5_ST_SZ_BYTES(mnvda_reg) - \
MLX5_BYTE_OFF(mnvda_reg, configuration_item_data))
@@ -195,6 +208,30 @@ mlx5_nv_param_read_sw_offload_conf(struct mlx5_core_dev *dev, void *mnvda,
return mlx5_nv_param_read(dev, mnvda, len);
}

+static int
+mlx5_nv_param_read_sw_offload_cap(struct mlx5_core_dev *dev, void *mnvda,
+ size_t len)
+{
+ MLX5_SET_CFG_ITEM_TYPE(global, mnvda, type_class, 0);
+ MLX5_SET_CFG_ITEM_TYPE(global, mnvda, parameter_index,
+ MLX5_CLASS_0_CTRL_ID_NV_SW_OFFLOAD_CAP);
+ MLX5_SET_CFG_HDR_LEN(mnvda, nv_sw_offload_cap);
+
+ return mlx5_nv_param_read(dev, mnvda, len);
+}
+
+static int
+mlx5_nv_param_read_sw_accelerate_conf(struct mlx5_core_dev *dev, void *mnvda,
+ size_t len)
+{
+ MLX5_SET_CFG_ITEM_TYPE(global, mnvda, type_class, 0);
+ MLX5_SET_CFG_ITEM_TYPE(global, mnvda, parameter_index,
+ MLX5_CLASS_0_CTRL_ID_NV_SW_ACCELERATE_CONF);
+ MLX5_SET_CFG_HDR_LEN(mnvda, nv_sw_accelerate_conf);
+
+ return mlx5_nv_param_read(dev, mnvda, len);
+}
+
static const char *const
cqe_compress_str[] = { "balanced", "aggressive" };

@@ -269,6 +306,124 @@ mlx5_nv_param_devlink_cqe_compress_set(struct devlink *devlink, u32 id,
return mlx5_nv_param_write(dev, mnvda, sizeof(mnvda));
}

+enum swp_l4_csum_mode {
+ SWP_L4_CSUM_MODE_DEVICE_DEFAULT = 0,
+ SWP_L4_CSUM_MODE_FULL_CSUM = 1,
+ SWP_L4_CSUM_MODE_L4_ONLY = 2,
+};
+
+static const char *const
+ swp_l4_csum_mode_str[] = { "device_default", "full_csum", "l4_only" };
+
+static int
+mlx5_nv_param_devlink_swp_l4_csum_mode_get(struct devlink *devlink, u32 id,
+ struct devlink_param_gset_ctx *ctx,
+ struct netlink_ext_ack *extack)
+{
+ struct mlx5_core_dev *dev = devlink_priv(devlink);
+ u32 mnvda[MLX5_ST_SZ_DW(mnvda_reg)] = {};
+ u8 value = U8_MAX;
+ void *data;
+ int err;
+
+ err = mlx5_nv_param_read_sw_accelerate_conf(dev, mnvda, sizeof(mnvda));
+ if (err) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "Failed to read sw_accelerate_conf mnvda reg");
+ return err;
+ }
+
+ data = MLX5_ADDR_OF(mnvda_reg, mnvda, configuration_item_data);
+ value = MLX5_GET(nv_sw_accelerate_conf, data, swp_l4_csum_mode);
+
+ if (value >= ARRAY_SIZE(swp_l4_csum_mode_str)) {
+ NL_SET_ERR_MSG_FMT_MOD(extack,
+ "Invalid swp_l4_csum_mode value %u read from device",
+ value);
+ return -EINVAL;
+ }
+
+ strscpy(ctx->val.vstr, swp_l4_csum_mode_str[value],
+ sizeof(ctx->val.vstr));
+ return 0;
+}
+
+static int
+mlx5_nv_param_devlink_swp_l4_csum_mode_validate(struct devlink *devlink, u32 id,
+ union devlink_param_value val,
+ struct netlink_ext_ack *extack)
+{
+ struct mlx5_core_dev *dev = devlink_priv(devlink);
+ u32 cap[MLX5_ST_SZ_DW(mnvda_reg)] = {};
+ void *data;
+ int err, i;
+
+ for (i = 0; i < ARRAY_SIZE(swp_l4_csum_mode_str); i++) {
+ if (!strcmp(val.vstr, swp_l4_csum_mode_str[i]))
+ break;
+ }
+
+ if (i >= ARRAY_SIZE(swp_l4_csum_mode_str)) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "Invalid value, supported values are device_default/full_csum/l4_only");
+ return -EINVAL;
+ }
+
+ if (i == SWP_L4_CSUM_MODE_L4_ONLY) {
+ err = mlx5_nv_param_read_sw_offload_cap(dev, cap, sizeof(cap));
+ if (err) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "Failed to read sw_offload_cap");
+ return err;
+ }
+
+ data = MLX5_ADDR_OF(mnvda_reg, cap, configuration_item_data);
+ if (!MLX5_GET(nv_sw_offload_cap, data, swp_l4_csum_mode_l4_only)) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "l4_only mode is not supported on this device");
+ return -EOPNOTSUPP;
+ }
+ }
+
+ return 0;
+}
+
+static int
+mlx5_nv_param_devlink_swp_l4_csum_mode_set(struct devlink *devlink, u32 id,
+ struct devlink_param_gset_ctx *ctx,
+ struct netlink_ext_ack *extack)
+{
+ struct mlx5_core_dev *dev = devlink_priv(devlink);
+ u32 mnvda[MLX5_ST_SZ_DW(mnvda_reg)] = {};
+ void *data;
+ u8 value;
+ int err;
+
+ if (!strcmp(ctx->val.vstr, "device_default"))
+ value = SWP_L4_CSUM_MODE_DEVICE_DEFAULT;
+ else if (!strcmp(ctx->val.vstr, "full_csum"))
+ value = SWP_L4_CSUM_MODE_FULL_CSUM;
+ else
+ value = SWP_L4_CSUM_MODE_L4_ONLY;
+
+ err = mlx5_nv_param_read_sw_accelerate_conf(dev, mnvda, sizeof(mnvda));
+ if (err) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "Failed to read sw_accelerate_conf mnvda reg");
+ return err;
+ }
+
+ data = MLX5_ADDR_OF(mnvda_reg, mnvda, configuration_item_data);
+ MLX5_SET(nv_sw_accelerate_conf, data, swp_l4_csum_mode, value);
+
+ err = mlx5_nv_param_write(dev, mnvda, sizeof(mnvda));
+ if (err)
+ NL_SET_ERR_MSG_MOD(extack,
+ "Failed to write sw_accelerate_conf mnvda reg");
+
+ return err;
+}
+
static int mlx5_nv_param_read_global_pci_conf(struct mlx5_core_dev *dev,
void *mnvda, size_t len)
{
@@ -548,6 +703,12 @@ static const struct devlink_param mlx5_nv_param_devlink_params[] = {
mlx5_nv_param_devlink_cqe_compress_get,
mlx5_nv_param_devlink_cqe_compress_set,
mlx5_nv_param_devlink_cqe_compress_validate),
+ DEVLINK_PARAM_DRIVER(MLX5_DEVLINK_PARAM_ID_SWP_L4_CSUM_MODE,
+ "swp_l4_csum_mode", DEVLINK_PARAM_TYPE_STRING,
+ BIT(DEVLINK_PARAM_CMODE_PERMANENT),
+ mlx5_nv_param_devlink_swp_l4_csum_mode_get,
+ mlx5_nv_param_devlink_swp_l4_csum_mode_set,
+ mlx5_nv_param_devlink_swp_l4_csum_mode_validate),
};

int mlx5_nv_param_register_dl_params(struct devlink *devlink)
--
2.47.3