net: mana: Cache MANA_QUERY_LINK_CONFIG result to avoid repeated HWC queries

mana_query_link_cfg() sends an HWC command to firmware on every call,
but the link speed and QoS values it returns only change when the
driver explicitly calls mana_set_bw_clamp(). This function is called
not only by userspace via ethtool get_link_ksettings, but also
periodically by hv_netvsc through netvsc_get_link_ksettings and by
the sysfs speed_show attribute via dev_attr_show, resulting in
unnecessary HWC traffic every few minutes.

Add a link_cfg_error field to mana_port_context to cache the query
result. The field uses three states: 1 (not yet queried, initial
value set during mana_probe_port), 0 (success, speed/max_speed are
valid), or a negative errno for permanent errors like -EOPNOTSUPP
when the hardware does not support the command. Transient errors and
qos_unconfigured responses are not cached so that subsequent calls
will retry.

MANA is ops-locked because it implements net_shaper_ops, so the core
already takes netdev_lock() around all ethtool_ops and net_shaper_ops
entry points. Reuse that lock to serialize mana_query_link_cfg() and
mana_set_bw_clamp(). This prevents a concurrent mana_set_bw_clamp()
from racing with an in-flight query and publishing stale pre-clamp
speed/max_speed.

Invalidate the cache inside mana_set_bw_clamp() on success, so all
current and future callers that change the link configuration
automatically trigger a fresh query on the next mana_query_link_cfg()
call. Also reset link_cfg_error during resume in mana_probe() under
netdev_lock(), so that any query already in flight cannot later
store 0 and silently overwrite the post-resume invalidation.

Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Link: https://patch.msgid.link/20260606133301.2180073-1-ernis@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index beada8660258a092d1dc6eda0090e19c32daf546..26aef21c6c2c89406fd89e5e18ef7f554b4c5961 100644 (file)
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1473,6 +1473,12 @@ int mana_query_link_cfg(struct mana_port_context *apc)
        struct mana_query_link_config_req req = {};
        int err;
 
+       netdev_assert_locked(ndev);
+
+       err = apc->link_cfg_error;
+       if (err <= 0)
+               return err;
+
        mana_gd_init_req_hdr(&req.hdr, MANA_QUERY_LINK_CONFIG,
                             sizeof(req), sizeof(resp));
 
@@ -1485,6 +1491,7 @@ int mana_query_link_cfg(struct mana_port_context *apc)
        if (err) {
                if (err == -EOPNOTSUPP) {
                        netdev_info_once(ndev, "MANA_QUERY_LINK_CONFIG not supported\n");
+                       apc->link_cfg_error = err;
                        return err;
                }
                netdev_err(ndev, "Failed to query link config: %d\n", err);
@@ -1502,12 +1509,12 @@ int mana_query_link_cfg(struct mana_port_context *apc)
                return err;
        }
 
-       if (resp.qos_unconfigured) {
-               err = -EINVAL;
-               return err;
-       }
+       if (resp.qos_unconfigured)
+               return -EINVAL;
+
        apc->speed = resp.link_speed_mbps;
        apc->max_speed = resp.qos_speed_mbps;
+       apc->link_cfg_error = 0;
        return 0;
 }
 
@@ -1519,6 +1526,8 @@ int mana_set_bw_clamp(struct mana_port_context *apc, u32 speed,
        struct net_device *ndev = apc->ndev;
        int err;
 
+       netdev_assert_locked(ndev);
+
        mana_gd_init_req_hdr(&req.hdr, MANA_SET_BW_CLAMP,
                             sizeof(req), sizeof(resp));
        req.vport = apc->port_handle;
@@ -1552,6 +1561,8 @@ int mana_set_bw_clamp(struct mana_port_context *apc, u32 speed,
        if (resp.qos_unconfigured)
                netdev_info(ndev, "QoS is unconfigured\n");
 
+       /* Invalidate the cache; next query will re-fetch from firmware. */
+       apc->link_cfg_error = 1;
        return 0;
 }
 
@@ -3518,6 +3529,7 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
        apc->port_handle = INVALID_MANA_HANDLE;
        apc->pf_filter_handle = INVALID_MANA_HANDLE;
        apc->port_idx = port_idx;
+       apc->link_cfg_error = 1;
        apc->cqe_coalescing_enable = 0;
 
        mutex_init(&apc->vport_mutex);
@@ -3834,6 +3846,9 @@ int mana_probe(struct gdma_dev *gd, bool resuming)
                        rtnl_lock();
                        apc = netdev_priv(ac->ports[i]);
                        enable_work(&apc->queue_reset_work);
+                       netdev_lock(ac->ports[i]);
+                       apc->link_cfg_error = 1;
+                       netdev_unlock(ac->ports[i]);
                        err = mana_attach(ac->ports[i]);
                        rtnl_unlock();
                        /* Log the port for which the attach failed, stop

diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index 5a9b94e0ef34f54f7a6e30a5d9358edd00cac99d..13c87baf018ee199fa57e90a767e053f64c6435b 100644 (file)
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -562,6 +562,10 @@ struct mana_port_context {
        u32 speed;
        /* Maximum speed supported by the SKU (mbps) */
        u32 max_speed;
+       /* 1 = not queried, 0 = cached success, negative = permanent error.
+        * Protected by the netdev instance lock.
+        */
+       int link_cfg_error;
 
        bool port_is_up;
        bool port_st_save; /* Saved port state */