Registering an MSI-x interrupt handler

I’m working on a storport miniport driver. I’m confused with the information I’m finding. In the storport interface I see that I register an MSI Interrupt handler in the PORT_CONFIGURATION_INFO during HwStorFindAdapter. But to get info on the message table I need to do IoConnectInterruptEx() which requires an MSI handler but it’s prototype is slightly different that the HwStorMSIInterrupt handler.

Can anyone shed some light for me on how you set an MSI-x up and if you use IoConnectInterruptEx and when?