Building Your Own Hardware Designs

This section will guide you through building a Xilinx Vitis-enabled U250 FPGA bitstream to run FireSim simulations.

Configuring a Build in the Manager

In the deploy/config_build.yaml file, you will notice that the builds_to_run section currently contains several lines, which indicates to the build system that you want to run all of these “build recipes” in parallel, with the parameters for each “build recipe” listed in the relevant section of the deploy/config_build_recipes.yaml file (or in the case of building a Chipyard target SoC in ${CY_DIR}/sims/firesim-staging/sample_config_build_recipes.yaml).

In this guide, we’ll build the default FireSim design for the Xilinx Vitis-enabled U250, which is specified by the vitis_firesim_rocket_singlecore_no_nic section in ${CY_DIR}/sims/firesim-staging/sample_config_build_recipes.yaml. This was the same configuration used to build the pre-built bitstream that you used to run simulations in the guide to running a simulation.

Looking at the vitis_firesim_rocket_singlecore_no_nic section in ${CY_DIR}/sims/firesim-staging/sample_config_build_recipes.yaml, there are a few notable items:

  • TARGET_CONFIG specifies that this configuration is a simple singlecore RISC-V Rocket with a single DRAM channel.

  • TARGET_PROJECT_MAKEFRAG specifies to the FireSim Make system how to build the TARGET_CONFIG.

  • bit_builder_recipe points to bit-builder-recipes/vitis.yaml, which is found in the deploy directory and tells the FireSim build system how to build bitstreams for this FPGA.

Having looked at this entry, let’s now set up the build in deploy/config_build.yaml. First, we’ll set up the build_farm mapping, which specifies the Build Farm Machines that are available to build FPGA bitstreams.

  • base_recipe will map to build-farm-recipes/externally_provisioned.yaml. This indicates to the FireSim manager that the machines used to run builds are existing machines that have been set up by the user, instead of cloud instances that are automatically provisioned.

  • default_build_dir is the directory in which builds will run out of on your Build Farm Machines. Change the default null to a path where you would like temporary build data to be stored on your Build Farm Machines.

  • build_farm_hosts is a section that contains a list of IP addresses or hostnames of machines in your Build Farm. By default, localhost is specified. If you are using a separate Build Farm Machine, you should replace this with the IP address or hostname of the Build Farm Machine on which you would like to run the build.

Having configured our Build Farm, let’s specify the design we’d like to build. To do this, edit the builds_to_run section in deploy/config_build.yaml so that it looks like the following:

builds_to_run:
    - vitis_firesim_rocket_singlecore_no_nic

In essence, you should delete or comment out all the other items in the builds_to_run section besides vitis_firesim_rocket_singlecore_no_nic.

Running the Build

Now, we can run a build like so (while also pointing to Chipyard’s recipes provided):

firesim buildbitstream -r -r ${CY_DIR}/sims/firesim-staging/sample_config_build_recipes.yaml

This will run through the entire build process, taking the Chisel (or Verilog) RTL and producing a bitstream that runs on the Xilinx Vitis-enabled U250 FPGA. This whole process will usually take a few hours. When the build completes, you will see a directory in deploy/results-build/, named after your build parameter settings, that contains all of the outputs of the Xilinx Vitis build process. Additionally, the manager will print out a path to a log file that describes everything that happened, in-detail, during this run (this is a good file to send us if you encounter problems).

The manager will also print an entry that can be added to config_hwdb.yaml so that the bitstream can be used to run simulations. This entry will contain a bitstream_tar key whose value is the path to the final generated bitstream file. You can share generated bitstreams with others by sharing the file listed in bitstream_tar and the config_hwdb.yaml entry for it.

Now that you know how to generate your own FPGA image, you can modify the target-design to add your own features, then build a FireSim-compatible FPGA image automatically!

This is the end of the Getting Started Guide. To learn more advanced FireSim features, you can choose a link under the “Advanced Docs” section to the left.