net/mlx5: implement swp_l4_csum_mode via devlink params

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

Supported values:
  1. default: device will choose between full_csum or l4_only. Driver
     will discover the device's choice during initialization.
  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.

Note that 'default' might be returned from the device and passed to
userspace, and it might also be set during a
devlink_param::reset_default() call, but attempts to set a value of
default directly with param-set will be rejected.

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

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20251119025038.651131-5-daniel.zahka@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/devlink/mlx5.rst

@@ -218,6 +218,20 @@ 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.
+
+       * ``default`` : Use the device's default checksum calculation
+         mode. The driver will discover during init whether or
+         full_csum or l4_only is in use. Setting this value explicitly
+         from userspace is not allowed, but some firmware versions may
+         return this value on param read.
+       * ``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

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 {

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,
 };
@@ -32,6 +34,12 @@ union mlx5_ifc_config_item_type_auto_bits {
 	u8 reserved_at_0[0x20];
 };
 
+enum {
+	MLX5_ACCESS_MODE_NEXT = 0,
+	MLX5_ACCESS_MODE_CURRENT,
+	MLX5_ACCESS_MODE_DEFAULT,
+};
+
 struct mlx5_ifc_config_item_bits {
 	u8         valid[0x2];
 	u8         priority[0x2];
@@ -123,6 +131,17 @@ 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 +214,32 @@ 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, int access_mode)
+{
+	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);
+	MLX5_SET(mnvda_reg, mnvda, configuration_item_header.access_mode,
+		 access_mode);
+
+	return mlx5_nv_param_read(dev, mnvda, len);
+}
+
 static const char *const
 	cqe_compress_str[] = { "balanced", "aggressive" };
 
@@ -269,6 +314,182 @@ 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_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[] = { "default", "full_csum", "l4_only" };
+
+static int
+mlx5_swp_l4_csum_mode_get(struct devlink *devlink, u32 id,
+			  int access_mode, u8 *value,
+			  struct netlink_ext_ack *extack)
+{
+	struct mlx5_core_dev *dev = devlink_priv(devlink);
+	u32 mnvda[MLX5_ST_SZ_DW(mnvda_reg)] = {};
+	void *data;
+	int err;
+
+	err = mlx5_nv_param_read_sw_accelerate_conf(dev, mnvda, sizeof(mnvda),
+						    access_mode);
+	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;
+	}
+
+	return 0;
+}
+
+static int
+mlx5_devlink_swp_l4_csum_mode_get(struct devlink *devlink, u32 id,
+				  struct devlink_param_gset_ctx *ctx,
+				  struct netlink_ext_ack *extack)
+{
+	u8 value;
+	int err;
+
+	err = mlx5_swp_l4_csum_mode_get(devlink, id, MLX5_ACCESS_MODE_NEXT,
+					&value, extack);
+	if (err)
+		return err;
+
+	strscpy(ctx->val.vstr, swp_l4_csum_mode_str[value],
+		sizeof(ctx->val.vstr));
+	return 0;
+}
+
+static int
+mlx5_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) ||
+	    i == SWP_L4_CSUM_MODE_DEFAULT) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "Invalid value, supported values are 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_swp_l4_csum_mode_set(struct devlink *devlink, u32 id, u8 value,
+			  struct netlink_ext_ack *extack)
+{
+	struct mlx5_core_dev *dev = devlink_priv(devlink);
+	u32 mnvda[MLX5_ST_SZ_DW(mnvda_reg)] = {};
+	void *data;
+	int err;
+
+	err = mlx5_nv_param_read_sw_accelerate_conf(dev, mnvda, sizeof(mnvda),
+						    MLX5_ACCESS_MODE_NEXT);
+	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_devlink_swp_l4_csum_mode_set(struct devlink *devlink, u32 id,
+				  struct devlink_param_gset_ctx *ctx,
+				  struct netlink_ext_ack *extack)
+{
+	u8 value;
+
+	if (!strcmp(ctx->val.vstr, "full_csum"))
+		value = SWP_L4_CSUM_MODE_FULL_CSUM;
+	else
+		value = SWP_L4_CSUM_MODE_L4_ONLY;
+
+	return mlx5_swp_l4_csum_mode_set(devlink, id, value, extack);
+}
+
+static int
+mlx5_devlink_swp_l4_csum_mode_get_default(struct devlink *devlink, u32 id,
+					  struct devlink_param_gset_ctx *ctx,
+					  struct netlink_ext_ack *extack)
+{
+	u8 value;
+	int err;
+
+	err = mlx5_swp_l4_csum_mode_get(devlink, id, MLX5_ACCESS_MODE_DEFAULT,
+					&value, extack);
+	if (err)
+		return err;
+
+	strscpy(ctx->val.vstr, swp_l4_csum_mode_str[value],
+		sizeof(ctx->val.vstr));
+	return 0;
+}
+
+static int
+mlx5_devlink_swp_l4_csum_mode_set_default(struct devlink *devlink, u32 id,
+					  enum devlink_param_cmode cmode,
+					  struct netlink_ext_ack *extack)
+{
+	u8 value;
+	int err;
+
+	err = mlx5_swp_l4_csum_mode_get(devlink, id, MLX5_ACCESS_MODE_DEFAULT,
+					&value, extack);
+	if (err)
+		return err;
+
+	return mlx5_swp_l4_csum_mode_set(devlink, id, value, extack);
+}
+
 static int mlx5_nv_param_read_global_pci_conf(struct mlx5_core_dev *dev,
 					      void *mnvda, size_t len)
 {
@@ -548,6 +769,14 @@ 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_WITH_DEFAULTS(MLX5_DEVLINK_PARAM_ID_SWP_L4_CSUM_MODE,
+					   "swp_l4_csum_mode", DEVLINK_PARAM_TYPE_STRING,
+					   BIT(DEVLINK_PARAM_CMODE_PERMANENT),
+					   mlx5_devlink_swp_l4_csum_mode_get,
+					   mlx5_devlink_swp_l4_csum_mode_set,
+					   mlx5_devlink_swp_l4_csum_mode_validate,
+					   mlx5_devlink_swp_l4_csum_mode_get_default,
+					   mlx5_devlink_swp_l4_csum_mode_set_default),
 };
 
 int mlx5_nv_param_register_dl_params(struct devlink *devlink)