antoineco / kernel-devel-vm-action

Bootstraps a Lima instance with the selected Linux kernel version for building and testing kernel modules.

Kernel Devel VM Action

A GitHub Action that bootstraps a Lima instance running Fedora Linux with the selected kernel version.

Its main purpose is to facilitate the building and testing of kernel modules in CI workflows. It was originally written to support the automated build pipeline for the broadcom-wl wireless driver.

How It Works

The Action queries Fedora's public mirrors to retrieve the latest QEMU image and SHA256 checksum for the selected OS version, and generates a Lima instance configuration using this information.

It then mounts provisioning scripts inside that instance, which Lima executes as part of its initialization process (cloud-init). The scripts query Bodhi — Fedora's updates system — to find and download the most suitable kernel candidate for the selected version. If a candidate is found, it is installed and the bootloader configuration gets updated to boot on that specific kernel version.

Usage

Pre-requisites

• A runner with Virtualization enabled, to support QEMU/KVM
• Lima ≥ 0.12.x
• yq ≥ 4.x

Inputs

• kernel (required): The desired kernel version in <major>.<minor> semantic format (e.g. "5.19").
• os: The version code of the Fedora Linux release to bootstrap the instance with (e.g. "f38"). Defaults to f39.

Outputs

• kernel: The full version string of the kernel running inside the bootstrapped instance (e.g. "5.19.17-300.fc37.x86_64").
• kernel-short: The short, SemVer compatible version string of the kernel running inside the bootstrapped instance (e.g. "5.19.17").
• logs: Location on the runner of the exported cloud-init logs (e.g. "/tmp/lima/myinstance").

Environment variables

Upon execution, this Action sets the LIMA_INSTANCE environment variable to the name of the bootstrapped Lima instance, and makes it available to all subsequent job steps.

Example workflow

name: Build Kernel Module

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    strategy:
      matrix:
        include:
        - kernel: '6.3'
          os: f37
        - kernel: '6.4'
          os: f38
        - kernel: '6.5'
          os: f39

    steps:
    - name: Bootstrap Lima instance
      id: builder
      uses: antoineco/kernel-devel-vm-action@v1
      with:
        kernel: ${{ matrix.kernel }}
        os: ${{ matrix.os }}

    - name: Build kernel module
      id: build
      run: lima make

For more elaborate usage examples, take a look at the build workflow for broadcom-wl, or the CI workflow for this Action.

kernel-devel-vm-action's Issues

Fedora Rawhide images can't be used with kernel versions other than latest

Fedora Rawhide images always ship with the latest Linux kernel, so using them with a kernel input value other than the absolute latest fails due to dnf / rpm refusing to downgrade the current kernel package(s).

Older builds can be downloaded from Bodhi without any issue, they just cannot be installed with the current method:

kernel-devel-vm-action/scripts/lib/builder/kernel.sh

Line 131 in 83523c6

dnf install -y "${rpms[@]}" || return