The Root Port MSI Base register contains the upper 32-bits of the 64-bit MSI address (described in the following table). For EP configurations, read returns zero.
|Bits||Name||Core Access||Reset Value||Description|
4 Kb-aligned address for MSI interrupts. In case of 32-bit MSI, it returns 0 but captures the upper 32-bits of the MSI address in case of 64-bit MSI.