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How to run a vAccel application using Unikraft

To run an image classification app in Unikraft using vAccel, we need:

  • an NVIDIA GPU which supports CUDA
  • the appropriate device drivers
  • jetson-inference

As long as we have the above depedencies, we can proceed setting up the vAccel environment for our example. A comprehensive walk through on installing the above dependencies is given in Jetson-inference.

Additionally, we will need to set up 3 components:

  • The vAccel Runtime system, vAccelrt on the bost
  • A hypervisor with vAccel support, in our case QEMU
  • and of course Unikraft

To make things easier we have created some scripts and Docketfiles which produce a vAccel enabled QEMU and a Unikraft unikernel. You can get them from this repo. The first 2 components can be built using the script with the -u option, like:

bash -u

The last component can be created using the script with the -u option, like:

bash -u

After succefully building all components we can just fire up our unikernel using the command:


This command will start Unikraft over QEMU classifying the image dog_0.jpg under guest/data/ directory of this repo.

Let's take a closer look on what is happening inside the containers and how we can perform each step by ourselves.

Setting up vAccert for the host

vAccelrt is a thin and efficient runtime system that links against the user application and is responsible for dispatching operations to the relevant hardware accelerators. In our case the backend plugin will be an NVIDIA GPU, and more specifically, jetson-inference, using TensorRT. As a result we need to build the Jetson plugin for vAccelrt.

At first let's get the source code:

git clone --recursive
cd vaccelrt 

As we mentioned before, we will also build the jetson plugin and we will specify ~/.local/ as the directory where vAccelrt will be installed.

mkdir build && cd build
make && make Install

Now that we have vAccelrt installed we need to set the plugin that we will use

export VACCEL_BACKENDS=/.local/lib/

Build QEMU with vAccel support

For the time being we have a seperated branch where QEMU exposes vAccel to the guest with legacy virtio. First lets get the source code:

git clone --recursive -b vaccelrt_legacy_virtio
cd qemu-vaccel

We will configure QEMU with only one target and we need to point out the install location of vAccelrt with cflags and ldflags. Please set the install prefix in case you do not want it to be installed in the default directory.

mkdir build && cd build
../configure --extra-cflags="-I /.local/include" --extra-ldflags="-L/.local/lib" --target-list=x86_64-softmmu --enable-virtfs
make -j12 && make install

THat's it. We are done with the host side!

Build the Unikraft application

We will follow the instructions from Unikraft's documentation with a minor change. We will not use the official Unikraft repo but our fork. In our fork we have added an example application for image classification.

git clone
mkdir apps/
cp -r unikraft/example apps/classify
cd apps/classify

Our example has a config which enables vAccel support for Unikraft and a lot of debug messages. You can use that config or you can make your own config, but make sure you select vaccelrt under library configuration inside menuconfig.

cp vaccel_config .config && make olddefconfig

After building is done, there will be a Unikraft image for KVM under the build directory.

Fire it up!

After that long journey of building let's see what we have done. Not yet...

One more thing. We need to get the model which will be used for the image classification. We will use a script which is already provided by jetson-inference (normally under `/usr/local/share/jetson-inference/tools. Also we need to point vAccel's jetson plugin the path to that model.

cp /usr/local/share/jetson-inference/data/networks/* networks
export VACCEL_IMAGENET_NETWORKS=/full/path/to/newly/downloaded/networks/directory

Finally we can run our unikernel using the command below:

LD_LIBRARY_PATH=/.local/lib:/usr/local/nvidia/lib:/usr/local/nvidia/lib64 qemu-system-x86_64 -cpu host -m 512 -enable-kvm -nographic -vga none \
    -fsdev local,id=myid,path=/data/data,security_model=none -device virtio-9p-pci,fsdev=myid,mount_tag=data,disable-modern=on,disable-legacy=off \
    -object acceldev-backend-vaccelrt,id=gen0 -device virtio-accel-pci,id=accl0,runtime=gen0,disable-legacy=off,disable-modern=on \
    -kernel /data/classify_kvm-x86_64 -append "vfs.rootdev=data -- dog_0.jpg 1"

Let's highlight some parts of the qemu command:

  • LD\_LIBRARY\_PATH environment variable: QEMU will dynamically link with every library it needs and in this case it also needs the vAccelrt library
  • -fsdev local,id=myid,path=./data,security\_model=none: We need to tell QEMU where will find the data that will pass to the guest. The data directory contains the image we want to classify
  • -object acceldev-backend-vaccelrt,id=gen0 -device virtio-accel-pci,id=accl0,runtime=gen0,disable-legacy=off,disable-modern=on: For the vAccel driver
  • -append "vfs.rootdev=data -- dog_0.jpg 1": In the command line we need to tell the classify application which image to classify and how many iterations to do