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neonvm-kernel

README.md

NeonVM kernel

We build a custom kernel in order to:

  1. Have support for unusual features that are only required for VMs (e.g. hotplugging, kvm-ptp clock synchronization, etc.)
  2. Avoid including features we don't need

Kernel images are all at neondatabase/vm-kernel:$tag, built by the vm-kernel github workflow.

Kernel images are typically assigned to a VM based on what was bundled in with the neonvm-runner in use, although this can be overridden on an individual VM basis using the .spec.guest.kernelImage field.

Upgrading the kernel

Assuming a plain upgrade (i.e. no additional features to enable), upgrading the kernel can be done with the following sequence of actions:

On amd64 (x64)

  1. On the host, run: 
    cd neonvm-kernel # this directory
docker build --build-arg KERNEL_VERSION=$NEW_VERSION --target build-deps -t kernel-build-deps -f Dockerfile.kernel-builder .
docker run --rm -v $PWD:/host --name kernel-build -it kernel-build-deps bash
  2. Then, inside the container, run: 
    cd linux-$NEW_VERSION
cp /host/linux-config-amd64-6.6.64 .config # Copy current config in
make menuconfig ARCH=x86_64
# do nothing; just save and exit, overwriting .config
cp .config /host/linux-config-amd64-$NEW_VERSION # NOTE: Different from existing!
  3. Back on the host, finish with: 
    # compare the two versions
diff linux-config-amd64-6.6.64 linux-config-amd64-$NEW_VERSION
# If all looks good, delete the old version. This is required so auto-selection works.
rm linux-config-amd64-6.6.64

On arm64 (aarch64 ARM)

  1. On the host, run: 
    cd neonvm-kernel # this directory
docker build --build-arg KERNEL_VERSION=$NEW_VERSION --target build-deps -t kernel-build-deps -f Dockerfile.kernel-builder .
docker run --rm -v $PWD:/host --name kernel-build -it kernel-build-deps bash
  2. Then, inside the container, run: 
    cd linux-$NEW_VERSION
cp /host/linux-config-aarch64-6.6.64 .config # Copy current config in
make menuconfig ARCH=arm64
# do nothing; just save and exit, overwriting .config
cp .config /host/linux-config-aarch64-$NEW_VERSION # NOTE: Different from existing!
  3. Back on the host, finish with: 
    # compare the two versions
diff linux-config-aarch64-6.6.64 linux-config-aarch64-$NEW_VERSION
# If all looks good, delete the old version. This is required so auto-selection works.
rm linux-config-aarch64-6.6.64

Afterwards, it's probably also good to do a search-and-replace repo-wide to update all places that mention the old kernel version.

Adjusting the config

To adjust the kernel config, try the following from this directory:

docker build --build-arg KERNEL_VERSION=6.6.64 --platform linux/x86_64 --target build-deps -t kernel-build-deps -f Dockerfile.kernel-builder .
docker run --rm -v $PWD:/host --name kernel-build -it kernel-build-deps bash
# inside that bash shell, do the menuconfig, then copy-out the config to /host