Introduction

This repository provides a minimal hardware-based demonstration of GPUDirect RDMA. This feature allows a PCIe device to directly access CUDA memory, thus allowing zero-copy sharing of data between CUDA and a PCIe device.

The code supports both:

• NVIDIA Jetson AGX Xavier (Jetson) running Linux for Tegra (L4T).

• A PC running the NVIDIA CUDA drivers and containing a Quadro or Tesla GPU.

A graphical representation of the system configuration created by the software in this repository, and the data flow between components, is shown below:

PCIe Device

Obtaining the Hardware

FPGA Board

PicoEVB is an M.2 form-factor FPGA board which attaches to the host's PCIe bus for application data transfer, and is programmed via the M.2 connector's USB bus. It is available from:

• picoevb.com.

• Amazon; search for ASIN "B0779PC8S4" or "PicoEVB".

PCIe Adapter Board

The PicoEVB board is a double-sided M.2 device. Jetson physically only supports boards with a full-size PCIe connector, or single-sided M.2 devices. PCs typically only support boards with a full-size PCIe connector. Some form of adapter is required to connect the two in a mechanically reliable way.

A PCIe x16/x8/x4/x2/x1 to M.2 key E adapter may be used to plug the PicoEVB board into a full-size PCIe slot on Jetson or a PC. One such adapter board may be available from Amazon as ASIN B013U4401W, product name "Sourcingbay M.2(NGFF) Wireless Card to PCI-e 1X Adapter".

The following pair of adapters may be used to connect the PicoEVB board to Jetson's M.2 key E connector:

• M.2 2230 key E to Mini-PCIe adapter with cable. This may be available from Amazon as ASIN B07JFYSNVL, product name "M.2 (NGFF) Key A/E/A+E to Mini PCI-E Adapter with FFC Cable". Alternatively, this may be available from Amazon as ASIN B00JSBPF70, product name "Bplus: P15S-P15F, M.2 (NGFF) to mPCIe Extender Board".

• Mini-PCIe to M.2 2230 adapter board. This may be available from Amazon as ASIN B07D4FCD1K, product name "HLT M.2 (NGFF) to mPCIe (PCIe+USB) Adapter".

The set of available adapters and vendors on Amazon is very variable over time. Some searching may be required to locate suitable adapters, from either Amazon or alternative websites.

Obtaining FPGA Programming Software

Xilinx Vivado Design Suite

This software must run on an x86 Linux PC.

Xilinx Vivado 2018.3 is used to compile the FPGA bitstream, and to program the bitstream into the FPGA. The free "WebPACK Edition" is sufficient. Obtain this software from the Xilinx website.

xvcd

This software must run on the system that the PicoEVB FPGA card is plugged into. This may be either an x86 Linux PC, or a Jetson system.

Vivado relies upon a piece of software known as xvcd (Xilinx Virtual Cable Daemon) to communicate with the PicoEVB board for programming purposes. Obtain it from github.com. Execute the commands below to download and compile the software:

sudo apt update
sudo apt install build-essential libftdi-dev
git clone https://github.com/RHSResearchLLC/xvcd.git
cd xvcd/
cd linux/src
make

Generating the Bitstream

A pre-compiled bitstream is provided in this project; fpga/picoevb.mcs. It is not necessary to regenerate the bitstream. However, if you wish to do so, follow these steps:

1. Open a shell prompt, and cd to the fpga/ directory in this project.

2. Execute ./git-to-project.sh to generate the Vivado project files. You may have to adjust the vivado variable in this script if the vivadoexecutable is not in your $PATH, or the expected installation location.

3. Run Vivado.

4. Open Vivado project fpga/vivado-project/vivado-project.xpr.

5. In the "PROJECT MANAGER" pane, expand "PROGRAM AND DEBUG", and click "Generate Bitstream". Click "Yes" to allow synthesis and implementation to run first, and "OK" to launch the generation process.

6. Wait until bitstream is complete; a pop-up dialog will appear. This will take from 5-30 minutes depending on the speed of your PC.

7. Close Vivado.

8. Go back to the shell prompt opened above, and execute./generate-cfgmem.sh. This generates the final programming file.

If you make modifications to the Vivado project, or any files or IP blocks it contains or uses, and wish to commit those changes into source control, execute./project-to-git.sh to regenerate the checked-in files git-to-project.tcland git-to-ips.tcl.

Programming the FPGA

Programming the FPGA requires Vivado installed on an x86 Linux PC, and xvcd running on the system that contains the PicoEVB board.

If you run xvcd on Jetson, you must allow network connections from Vivado on your x86 Linux PC to xvcd running on Jetson. The simplest way to do this is to use ssh's port-forwarding feature; on the x86 Linux PC, execute:

ssh -L 2542:127.0.0.1:2542 ip_address_of_jetson

To run xvcd, on the system containing the FPGA card, execute:

sudo ./xvcd -P 0x6015

On your x86 Linux PC, open a shell prompt, cd to the fpga/ directory in this project, and execute:

program-fpga.sh

The process of connecting Vivado's programming tools to the FPGA can be unreliable. If the connection attempt fails, and the script exits without programming the FPGA, you will need to execute the command again.

The programming process will take from 20 to 40 minutes. The programming process generates no output for most of its operation, so may appear to have hung, but is actually running.

Linux Kernel Driver

Building on Jetson, to Run on Jetson

To build the Linux kernel driver on Jetson, execute:

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/kernel-module/
./build-for-jetson-igpu-native.sh

This will generate picoevb-rdma.ko.

Building on an x86 Linux PC, to Run on Jetson

The Linux kernel driver may alternatively be built (cross-compiled) on an x86 Linux PC. You will first need to obtain a copy of the "Linux headers" or "kernel external module build tree" files from L4T; these may be found in/usr/src/ on Jetson, or obtained from the L4T downloads website.

To build the Linux kernel driver on a x86 Linux PC, execute:

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/kernel-module/
# Adjust the KDIR value to match the exact path in your copy of the
# kernel headers
KDIR=/path/to/linux-headers-4.9.140-tegra-linux_x86_64/kernel-4.9/ ./build-for-jetson-igpu-on-pc.sh

This will generate picoevb-rdma.ko. This file must be copied to Jetson.

Building on an x86 Linux PC, to Run on That PC

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/kernel-module/
./build-for-pc-native.sh

This will generate picoevb-rdma.ko.

Loading the Module

To load the kernel module, execute:

sudo insmod ./picoevb-rdma.ko

Once the module is loaded, executing lspci -v should show that the module is in use as the kernel driver for the FPGA board:

$ lspci -v
...
0003:01:00.0 Memory controller: NVIDIA Corporation Device 0001
	Subsystem: NVIDIA Corporation Device 0001
	Flags: bus master, fast devsel, latency 0, IRQ 36
	Memory at 34210000 (32-bit, non-prefetchable) [size=4K]
	Memory at 34200000 (32-bit, non-prefetchable) [size=64K]
	Capabilities: <access denied>
	Kernel driver in use: picoevb-rdma

User-space Applications

Building on Jetson, to Run on Jetson

The client applications are best built on Jetson itself. Make sure you have the CUDA development tools installed, and execute:

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/client-applications/
./build-for-jetson-igpu-native.sh

Building on an x86 Linux PC, to Run on Jetson

Building (cross-compiling) the client applications on a x86 Linux PC is only partially supported; the makefile does not yet support cross-compiling the CUDA test application. However, the other applications may be cross-compiled by executing:

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/client-applications/
./build-for-jetson-igpu-on-pc.sh

You may need to adjust the value of variable CROSS_COMPILE in script./build-for-jetson-igpu-on-pc.sh to match the configuration of your x86 Linux PC.

Building on an x86 Linux PC, to Run on That PC

Make sure you have the CUDA development tools installed, and execute:

sudo apt update
sudo apt install build-essential bc
cd /path/to/this/project/client-applications/
./build-for-pc-native.sh

Running the Tests

Data Access Tests

Two PCIe data access tests are provided; rdma-malloc and rdma-cuda. Both tests are structurally identical, but allocate memory using different APIs; the former using malloc(), and the latter via cudaHostAlloc() (Jetson) orcudaMalloc() (PC).

Both tests proceed as following:

1. Allocate source and destination memory.

2. In the CUDA case, prepare the memory for RDMA by callingcuPointerSetAttribute(CU_POINTER_ATTRIBUTE_SYNC_MEMOPS) and pinning it.

3. Fill the source surface with a known pattern.

4. Fill the destination surface with different values.

5. Use the FPGA to copy the source to the destination surface.

6. Validate that the data was correctly copied.

To run the tests, execute:

sudo ./rdma-malloc
sudo ./rdma-cuda

You can avoid the need to use sudo by applying appropriate permissions to the kernel driver's device file, /dev/picoevb.

Internally to the kernel driver, the copy operation divides the surface into 64KiB chunks (or smaller, depending on memory alignment), and for each chunk first copies that chunk's data from the source surface to the FPGA's internal memory, then copies the data from the FPGA's internal memory to the destination surface. This demonstrates both PCIe read and write access to CUDA GPU memory. The requirement to divide the data into chunks is a limitation of the internal memory size of the PicoEVB board's FPGA, and likely would not apply in a production device.

set-leds

This test sets the values of the three LEDs on the PicoEVB. It accepts a single command-line parameter indicating the binary value to display on those LEDs. The hardware inverts this value, so a parameter value of 0 turns on all LEDS, and a parameter value of 7 turns off all LEDs. For example:

./set-leds 2
./set-leds 5