Reads from this location return queued interrupt messages. Data from each read follows the format shown in Table: Root Port Interrupt FIFO Read Register 1 . For MSI interrupts, the message payload is presented in the Root Port Interrupt FIFO Read 2 register. The interrupt-handling flow should be to read this register first, immediately followed by the Root Port Interrupt FIFO Read 2 register. For non-Root Port cores, reads return zero.
Note: Reads are non-destructive. Removing the message from the FIFO requires a write to either this register or the Root Port Interrupt FIFO Read 2 register. The write value is ignored.