2.2. FPGA-Accelerated Simulation

2.2.1. FireSim

FireSim is an open-source cycle-accurate FPGA-accelerated full-system hardware simulation platform that runs on cloud FPGAs (Amazon EC2 F1). FireSim allows RTL-level simulation at orders-of-magnitude faster speeds than software RTL simulators. FireSim also provides additional device models to allow full-system simulation, including memory models and network models.

FireSim currently supports running only on Amazon EC2 F1 FPGA-enabled virtual instances. In order to simulate your Chipyard design using FireSim, if you have not already, follow the initial EC2 setup instructions as detailed in the FireSim documentation. Then clone Chipyard onto your FireSim manager instance, and setup your Chipyard repository as you would normally.

Next, initalize FireSim as a library in Chipyard by running:

# At the root of your chipyard repo
./scripts/firesim-setup.sh --fast

firesim-setup.sh initializes additional submodules and then invokes firesim’s build-setup.sh script adding --library to properly initialize FireSim as a library submodule in chipyard. You may run ./sims/firesim/build-setup.sh --help to see more options.

Finally, source the following environment at the root of the firesim directory:

cd sims/firesim
# (Recommended) The default manager environment (includes env.sh)
source sourceme-f1-manager.sh

Note

Every time you want to use FireSim with a fresh shell, you must source this sourceme-f1-manager.sh

At this point you’re ready to use FireSim with Chipyard. If you’re not already familiar with FireSim, please return to the FireSim Docs, and proceed with the rest of the tutorial.

2.2.1.1. Current Limitations:

FireSim integration in Chipyard is still a work in progress. Presently, you cannot build a FireSim simulator from any generator project in Chipyard except firechip, which properly invokes MIDAS on the target RTL.

In the interim, workaround this limitation by importing Config and Module classes from other generator projects into FireChip. For example, assuming you Chipyard config looks as following:

class CustomConfig extends Config(
  new WithInclusiveCache ++
  new myproject.MyCustomConfig ++
  new DefaultRocketConfig
)

Then the equivalent FireChip config (in generators/firechip/src/main/scala/TargetConfigs.scala) based on FireSimRocketChipConfig will look as follows:

class FireSimCustomConfig extends Config(
  new WithBootROM ++
  new WithPeripheryBusFrequency(BigInt(3200000000L)) ++
  new WithExtMemSize(0x400000000L) ++ // 16GB
  new WithoutTLMonitors ++
  new WithUARTKey ++
  new WithNICKey ++
  new WithBlockDevice ++
  new WithRocketL2TLBs(1024) ++
  new WithPerfCounters ++
  new WithoutClockGating ++
  new WithInclusiveCache ++
  new myproject.MyCustomConfig ++
  new freechips.rocketchip.system.DefaultConfig)

You should then be able to refer to those classes or an alias of them in your DESIGN or TARGET_CONFIG variables. Note that if your target machine has I/O not provided in the default FireChip targets (see generators/firechip/src/main/scala/Targets.scala) you may need to write a custom bridge.