Methods and apparatus for PASID-based routing extension for Scalable IOV systems. The system may include a Central Processing Unit (CPU) operatively coupled to a scalable Input/Output Virtualization (IOV) device via an in-line device such as a smart controller or accelerator. A Control Process Address Space Identifier (C-PASID) associated with a first memory space is implemented in an Assignable Device Interface (ADI) for the IOV device. The ADI also implements a Data PASID (D-PASID) associated with a second memory space in which data are stored. The C-PASID is used to fetch a descriptor in the first memory space and the D-PASID is employed to fetch data in the second memory space. A hub embedded on the in-line device or implemented as a discrete device is used to steer memory access requests and/or fetches to the CPU or to the in-line device using the C-PASID and D-PASID. IOV devices include multi-PASID helper devices and off-the-shelf devices such as NICs with modified ADIs to support C-PASID and D-PASID usage.