Direct connection of two InfiniBand ports without IB switch

I want to install two ConnectX-6(VPI) cards in each PC and then connect two infiniband ports directly.
When I googling, I’ve not seen a configuration without an IB switch, so I’d like to know if the switch is always required.

You can do it.

It will limit you to a 2-port subnet comprised of the 2 connected ports.