Interfacing Between PCIe and Infiniband
Infiniband and PCIe are related but very different. Even the link training state machine (LTSSM for PCIe) is different as is the method of determining whether a link partner is present.
They are both based on serial differential pairs that may be used as lanes on a single logical port (although the number of possible lane counts lanes is a bit different).
The packet structure for the two is not the same and the flow control although of the same principle is also different.
Even the type of interconnect is different (PCIe is a root complex with endpoints and Infiniband is a fabric).
So Infiniband and PCIe differ significantly both electrically and logically.
The bottom line is that you cannot just hook one up to the other; you will need a target channel  adapter (or host channel adapter which is more capable) on the Infiniband side with a processor that can then forward the data to the PCIe device.
Some devices from Mellanox cater for multiple protocols on different ports; whether there are any products that implement such a bridge is something I do not know.
You may find this comparison useful.