you can update your card firmware with an intermediate update found here release notes here in the .tgz file look for your card .ini file MHQH19B-XTR_A1-A3 this will update your card to firmware to Rev 2.9.1200.
i would try and update the ib card firmware if its a OEM then do a custom oem update.
i also tested this out on a x9srl-f board running esxi 6 4510822 with a ibm oem connectx-2 firmware ver 2.9.1200
Custom Firmware for Mellanox OEM Infiniband Cards - WS2012 RDMA
if the mellanox card is VPI then it defaults to infiniband not ethernet it should be plug n play and you would run the IB network separate from the ethernet network. in my home lab every server has dual 1gb for front end and dual 40gb IB connection for back end.
seen this on the bay and got one at $300 it has a built in subnet manager the condition is like brand new came with console cable and rails.
Mellanox MIS5035Q-1BRC 36-Port InfiniScale IV IS5035 QDR InfiniBand Switch | eBay