net/mlx5: Lag, split aggregate speed into oper and max helpers

mlx5_lag_sum_devices_speed computes the LAG aggregate by summing oper
speeds across all ports. This has two bugs.

First, it relies on the assumption that a port whose carrier is down
will report an oper speed of zero and therefore not contribute to the
sum. This assumption does not always hold: when the link partner
disconnects the port transitions to DOWN state but firmware may still
report a non-zero oper speed, causing the aggregate to include a port
that is not actively carrying traffic.

Second, in active-backup mode only one port transmits at a time, so
the aggregate should reflect a single port speed rather than the sum
of all ports.

Fix this by splitting mlx5_lag_sum_devices_speed into two helpers.
mlx5_lag_get_devices_oper_speed reflects the speed currently available:
it queries the vport state of each port and skips any port that is not
UP, rather than relying on oper speed being zero.
mlx5_lag_get_devices_max_speed is state-independent and returns the
maximum achievable speed used as a fallback when speed is 0; for
active-backup it takes the maximum single-port speed instead of the sum.

The bugs were discovered during integration and reproduced on a
back-to-back ConnectX-8 setup.

The first bug (stale oper speed when link goes down) was observed: after
the link partner disconnected, the aggregate TX speed reported to vports
remained full speed because firmware still returned the last oper speed,
causing vports to be rate-limited to the old aggregate speed.

The second bug (active-backup summing all port speeds instead of the
active port's speed) was also triggered: in active-backup mode the
computed aggregate was double the expected value since both port speeds
were summed even though only one port was active.

Fixes: 28ea6036dad2 ("net/mlx5: Handle port and vport speed change events in MPESW")
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Shay Drori <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260930170406.148548-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions