Enabling VirtIO Driver Support on FPGAs

Host-FPGA connectivity is critical for enabling a vast number of FPGA use cases in data centers, edge, and IoT. This interface must be reliable, robust, and uniform, whilst supporting necessary protocols and functionality. However, existing support for host-FPGA connectivity has several drawbacks on both the host and the device. This includes a lack of portability and poor upstream support, both of which can make it difficult for CPUs to easily and effectively leverage FPGAs. Native VirtIO drivers in the host operating system can help address some of these limitations, especially on the host side, but implementing device-side support for the VirtIO specification is a challenge due to the substantial hardware complexity involved. In this work, we present a framework for enabling FPGAs to interface native operating system VirtIO drivers on the host. To reduce the implementation overhead and improve portability, this framework uses both generic RTL blocks and modified, chip/device specific PCIe IP blocks. Moreover, this approach implements all the necessary data structures and functionality needed to meet the VirtIO specification requirements. We test the framework using the Xilinx DMA/Bridge Subsystem for PCI Express (XDMA) IP, implemented on an Alinx AX7A200 FPGA board (with a Xilinx XC7A200TFBG484-2 FPGA chip), and a host machine running the Fedora operating system. Our results show that the FPGA can be successfully enumerated as a VirtIO device, and interfaced using only native Linux VirtIO drivers.