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Virtio Accel

Virtio Accel was inspired by the Virtio Crypto paravirtual device for enabling accelerated crypto operations inside a Virtual Machine.

We extended the idea of accelerated crypto operations to any acceleratable operation, which resulted in the virtio-accel module and the corresponding vAccelRT plugin that uses it to allow vAccel applications to use accelerated operations from within a Virtual Machine. Currently we support the AWS Firecracker and QEMU hypervisors.

Building the kernel module

We first need to build the virtio-accel module that will be used inside our VM. We will need the source of the kernel module and a kernel tree.


For Firecracker we use Linux kernel version 4.20, because that is consistent with the configuration the AWS Firecracker team is shipping but the module itself should be able to build with newer kernel versions, as well. For example, for our k8s deployment of vAccel we use Linux Kernel version 5.4.60

Let's fetch and build the kernel

# Fetch the Linux kernel tree
git clone --depth=1 -b v4.20

cd linux

# Fetch the Firecracker config
wget -O arch/x86/configs/microvm.config

touch .config
make microvm.config
make vmlinux

cd ..
ls linux/vmlinux

You should now have a newly built kernel image under linux/vmlinux, which you can use to boot with your Firecracker VM.

And now we can build the module:

git clone
make -C virtio-accel KDIR=$(pwd)/linux ZC=0
ls virtio-accel/virtio_accel.ko

This should build the module under virtio-accel/virtio_accel.ko.

Note: The virtio-accel module supports zero-copy operations. This functionality has not been implemented yet in Firecracker, so we disabled the feature passing ZC=0 to the Makefile.



Building the vAccelRT plugin

The vAccelRT runtime ships with a virtio plugin which speaks the virtio-accel module's ioctl language to offload computation from a VM guest to the host.

# Fetch the vAccelRT repo
git clone --recursive
cd vaccelrt

mkdir build
cd build
cmake .. -DBUILD_PLUGIN_VIRTIO=ON -DVIRTIO_ACCEL_ROOT=../../virtio-accel

cd ../../
ls vaccelrt/build/plugins/virtio/

This builds the plugin and places it under vaccelrt/build/plugins/virtio/ You can now insert the plugin to your VMs rootfs and run a vAccel application.