The purpose of the KB is to point the reader into proper direction based on the reader’s need :

Melannox can be configured in either Infiniband mode or Ethernet mode, based on the HCA.


If you intend to use IB in your virtual machines, then you should follow this KB :
/faq/index.php?action=artikel&cat=24&id=361&artlang=en
If your goal is to use Ethernet then you can follow this KB to integrate neutron with Mellanox Ethernet ports :
/faq/index.php?action=artikel&cat=24&id=238&artlang=en


If you do not intend to virtualize your Mellanox HCA and use it within your virtual environment, but yet you want to reap the benefits of your IB cards for your tenant networks, then please follow this KB article :
/faq/index.php?action=artikel&cat=24&id=326&artlang=en