net/mlx4_core: Zero out lkey field in SW2HW_MPT fw command

When re-registering a user mr, the mpt information for the
existing mr when running SRIOV is obtained via the QUERY_MPT
fw command. The returned information includes the mpt's lkey.

This retrieved mpt information is used to move the mpt back
to hardware ownership in the rereg flow (via the SW2HW_MPT
fw command when running SRIOV).

The fw API spec states that for SW2HW_MPT, the lkey field
must be zero. Any ConnectX-3 PF driver which checks for strict spec
adherence will return failure for SW2HW_MPT if the lkey field is not
zero (although the fw in practice ignores this field for SW2HW_MPT).

Thus, in order to conform to the fw API spec, set the lkey field to zero
before invoking SW2HW_MPT when running SRIOV.

Fixes: e630664c ("mlx4_core: Add helper functions to support MR re-registration")
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/mr.c

@@ -363,6 +363,7 @@ int mlx4_mr_hw_write_mpt(struct mlx4_dev *dev, struct mlx4_mr *mmr,
 			container_of((void *)mpt_entry, struct mlx4_cmd_mailbox,
 				     buf);
 
+		(*mpt_entry)->lkey = 0;
 		err = mlx4_SW2HW_MPT(dev, mailbox, key);
 	}