ACCFS – Virtual File System Support for Host Coupled Run-Time Reconfigurable FPGAs.

In this paper a solution for the integration of FPGAs into host systems is presented. For managing user requests targeting FPGA tasks, including configuration and communication, the software framework ACCFS (ACCelerator File System) is utilized, which is built on a virtual file system (VFS). Such a system can be used for offloading compute kernels on the FPGA. Applying run-time reconfiguration on dynamically and partially reconfigurable (DPR) FPGAs allows to build plug-in FPGA solutions, consisting only of a single FPGA, without the need of external bridges or a second FPGA to handle host communication. Run-time reconfiguration also enables multi user and multi context support on the FPGA based on the VFS approach. Run-time reconfigurable modules (RTRMs) allow FPGA module creation on demand by the user. For the implementation on a Hyper-Transport (HT) coupled FPGA, the HT cave was extended in such a way that it provides an infrastructure for dealing with multiple run-time reconfigurable modules. In a case study two distinct compute kernel offload functions are implemented as RTRMs. Multiple instances of these RTRMs can be provided to the user on demand during run-time.