Merge branch 'net-mlx5-preserve-speed-and-state-across-vport-modify-commands'

Tariq Toukan says:

====================
net/mlx5: Preserve speed and state across vport modify commands

The firmware vport modify command bundles both admin state and max tx
speed in a single operation, which requires each side to preserve the
other field when it only intends to change one.

When modifying max tx speed, the driver already queries the current
admin state and passes it back to avoid overwriting it. However, this
query and the subsequent modify were not atomic, a state change
between the two could cause the modify to overwrite the new state with
a stale value. The fix holds esw->state_lock across the query-modify
sequence.

When support for setting max tx speed via the vport modify command was
introduced, the existing admin state modify path was not updated to
preserve the current speed. As a result, the firmware interprets the
zero speed field as an intentional reset. The fix adds a speed query
before the state modify and passes the result back in the command.

To support that, mlx5_query_vport_max_tx_speed() had to be fixed first:
it was returning zero whenever the vport was DOWN, which was correct
for the query_port_speed verb but would defeat the purpose of querying
before a state modify. The DOWN-to-zero logic is moved to the
verb-layer caller so the function returns the raw firmware value.

Patch #1  holds esw->state_lock across the state query and modify in
          the speed modify path
Patch #2  moves the vport DOWN zero mapping to the verb-layer caller
          so the query returns the raw firmware value
Patch #3  queries current max tx speed before modifying vport state to
          preserve it
====================

Link: https://patch.msgid.link/20260816065015.3280733-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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