From: Mohammad Heib <[email protected]>

Add support for the new generic devlink runtime parameter
"max_mac_per_vf", which controls the maximum number of MAC addresses
a trusted VF can use.

By default (value 0), the driver enforces its internally calculated
per-VF MAC filter limit. A non-zero value acts as a strict cap,
overriding the internal calculation.

Please note that the configured value is only a theoretical maximum
and a hardware limits may still apply.

- Previous discussion about this change:
  https://lore.kernel.org/netdev/[email protected]
  https://lore.kernel.org/netdev/[email protected]

Signed-off-by: Mohammad Heib <[email protected]>
---
 Documentation/networking/devlink/i40e.rst     | 35 ++++++++++++++
 drivers/net/ethernet/intel/i40e/i40e.h        |  4 ++
 .../net/ethernet/intel/i40e/i40e_devlink.c    | 48 ++++++++++++++++++-
 .../ethernet/intel/i40e/i40e_virtchnl_pf.c    | 28 +++++++----
 4 files changed, 103 insertions(+), 12 deletions(-)

diff --git a/Documentation/networking/devlink/i40e.rst 
b/Documentation/networking/devlink/i40e.rst
index d3cb5bb5197e..3052f638fdd5 100644
--- a/Documentation/networking/devlink/i40e.rst
+++ b/Documentation/networking/devlink/i40e.rst
@@ -7,6 +7,41 @@ i40e devlink support
 This document describes the devlink features implemented by the ``i40e``
 device driver.
 
+Parameters
+==========
+
+.. list-table:: Generic parameters implemented
+    :widths: 5 5 90
+
+    * - Name
+      - Mode
+      - Notes
+    * - ``max_mac_per_vf``
+      - runtime
+      - Controls the maximum number of MAC addresses a **trusted VF** can use
+        on i40e devices.
+
+        By default (``0``), the driver enforces its internally calculated 
per-VF
+        MAC filter limit, which is based on the number of allocated VFS.
+
+        If set to a non-zero value, this parameter acts as a strict cap:
+        the driver will use the user-provided value instead of its internal
+        calculation.
+
+        **Important notes:**
+        - MAC filters are a **shared hardware resource** across all VFs.
+          Setting a high value may cause other VFs to be starved of filters.
+
+        - This value is a **theoretical maximum**. The hardware may return
+          errors when its absolute limit is reached, regardless of the value
+          set here.
+
+        - Only **trusted VFs** are affected; untrusted VFs use a fixed small
+          limit.
+
+        The default value is ``0`` (internal calculation is used).
+
+
 Info versions
 =============
 
diff --git a/drivers/net/ethernet/intel/i40e/i40e.h 
b/drivers/net/ethernet/intel/i40e/i40e.h
index 801a57a925da..d2d03db2acec 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -574,6 +574,10 @@ struct i40e_pf {
        struct i40e_vf *vf;
        int num_alloc_vfs;      /* actual number of VFs allocated */
        u32 vf_aq_requests;
+       /* If set to non-zero, the device uses this value
+        * as maximum number of MAC filters per VF.
+        */
+       u32 max_mac_per_vf;
        u32 arq_overflows;      /* Not fatal, possibly indicative of problems */
        struct ratelimit_state mdd_message_rate_limit;
        /* DCBx/DCBNL capability for PF that indicates
diff --git a/drivers/net/ethernet/intel/i40e/i40e_devlink.c 
b/drivers/net/ethernet/intel/i40e/i40e_devlink.c
index cc4e9e2addb7..cd01e35da94e 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_devlink.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_devlink.c
@@ -5,6 +5,35 @@
 #include "i40e.h"
 #include "i40e_devlink.h"
 
+static int i40e_max_mac_per_vf_set(struct devlink *devlink,
+                                  u32 id,
+                                  struct devlink_param_gset_ctx *ctx,
+                                  struct netlink_ext_ack *extack)
+{
+       struct i40e_pf *pf = devlink_priv(devlink);
+
+       pf->max_mac_per_vf = ctx->val.vu32;
+       return 0;
+}
+
+static int i40e_max_mac_per_vf_get(struct devlink *devlink,
+                                  u32 id,
+                                  struct devlink_param_gset_ctx *ctx)
+{
+       struct i40e_pf *pf = devlink_priv(devlink);
+
+       ctx->val.vu32 = pf->max_mac_per_vf;
+       return 0;
+}
+
+static const struct devlink_param i40e_dl_params[] = {
+       DEVLINK_PARAM_GENERIC(MAX_MAC_PER_VF,
+                             BIT(DEVLINK_PARAM_CMODE_RUNTIME),
+                             i40e_max_mac_per_vf_get,
+                             i40e_max_mac_per_vf_set,
+                             NULL),
+};
+
 static void i40e_info_get_dsn(struct i40e_pf *pf, char *buf, size_t len)
 {
        u8 dsn[8];
@@ -165,7 +194,18 @@ void i40e_free_pf(struct i40e_pf *pf)
  **/
 void i40e_devlink_register(struct i40e_pf *pf)
 {
-       devlink_register(priv_to_devlink(pf));
+       struct devlink *dl = priv_to_devlink(pf);
+       struct device *dev = &pf->pdev->dev;
+       int err;
+
+       err = devlink_params_register(dl, i40e_dl_params,
+                                     ARRAY_SIZE(i40e_dl_params));
+       if (err)
+               dev_err(dev,
+                       "devlink params register failed with error %d", err);
+
+       devlink_register(dl);
+
 }
 
 /**
@@ -176,7 +216,11 @@ void i40e_devlink_register(struct i40e_pf *pf)
  **/
 void i40e_devlink_unregister(struct i40e_pf *pf)
 {
-       devlink_unregister(priv_to_devlink(pf));
+       struct devlink *dl = priv_to_devlink(pf);
+
+       devlink_unregister(dl);
+       devlink_params_unregister(dl, i40e_dl_params,
+                                 ARRAY_SIZE(i40e_dl_params));
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c 
b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
index 081a4526a2f0..e6d90d51221b 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
@@ -2935,19 +2935,26 @@ static inline int i40e_check_vf_permission(struct 
i40e_vf *vf,
                if (!f)
                        ++mac_add_cnt;
        }
-
-       /* If this VF is not privileged, then we can't add more than a limited
-        * number of addresses.
+       /* Determine the maximum number of MAC addresses this VF may use.
+        *
+        * - For untrusted VFs: use a fixed small limit.
+        *
+        * - For trusted VFs: limit is calculated by dividing total MAC
+        *  filter pool across all VFs/ports.
         *
-        * If this VF is trusted, it can use more resources than untrusted.
-        * However to ensure that every trusted VF has appropriate number of
-        * resources, divide whole pool of resources per port and then across
-        * all VFs.
+        * - User can override this by devlink param "max_mac_per_vf".
+        *   If set its value is used as a strict cap.
+        *   Note:
+        *    even when overridden, this is a theoretical maximum; hardware
+        *    may reject additional MACs if the absolute HW limit is reached.
         */
-       if (!vf_trusted)
+       if (!vf_trusted) {
                mac_add_max = I40E_VC_MAX_MAC_ADDR_PER_VF;
-       else
+       } else {
                mac_add_max = 
I40E_VC_MAX_MACVLAN_PER_TRUSTED_VF(pf->num_alloc_vfs, hw->num_ports);
+               if (pf->max_mac_per_vf > 0)
+                       mac_add_max = pf->max_mac_per_vf;
+       }
 
        /* VF can replace all its filters in one step, in this case mac_add_max
         * will be added as active and another mac_add_max will be in
@@ -2961,7 +2968,8 @@ static inline int i40e_check_vf_permission(struct i40e_vf 
*vf,
                        return -EPERM;
                } else {
                        dev_err(&pf->pdev->dev,
-                               "Cannot add more MAC addresses, trusted VF 
exhausted it's resources\n");
+                               "Cannot add more MAC addresses: trusted VF 
reached its maximum allowed limit (%d)\n",
+                               mac_add_max);
                        return -EPERM;
                }
        }
-- 
2.50.1

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