MSL Linux Kernel

This repository builds an arm64 Linux kernel for MSL and publishes versioned kernel releases.

MSL uses an unmodified Linux source release with Apple's 6.18 kernel configuration in configs/base.config and MSL-specific options in configs/msl.config. The MSL config enables,

• USB storage
• quotas
• NFS
• device mapper
• NBD
• KVM
• 16 KiB pages

Why the kernel uses 16 KiB pages

Heavy macOS swap pressure repeatedly corrupts the guest Linux kernel within minutes and kills the VM. The hypothesis is that, with 4 KiB guest pages on a 16 KiB host, each host page backs four 4 KiB stage-2 entries, and guest TLB invalidations go through a workaround. If a compression burst evicts a host page and not every stage-2 translation, or an emulated TLBI, is invalidated, a vCPU keeps a stale translation. It then writes to a physical page that now belongs to something else, and later sees the restored (old or zeroed) page. See #48.

Build locally

On macOS, install Apple's container CLI, then run:

./scripts/build.sh

The script builds Linux 6.18.15 in a Debian trixie arm64 container. Set KVER to build another Linux 6.18.x release. The build downloads the matching kernel.org source archive.

To build on Debian or Ubuntu arm64 without the container wrapper, install required packages,

sudo apt install -y build-essential flex bison bc libelf-dev libssl-dev curl xz-utils cpio kmod python3

then run:

./scripts/build-linux.sh . out [linux-version]

The default version is 6.18.15. Both build methods write these files to out/:

• Image: arm64 kernel image.
• config: final kernel configuration.
• tag: release tag for these inputs.

To try the kernel in an MSL checkout, set MSL_KERNEL_OUT to this repository's out directory and run scripts/build.sh there.

Release a kernel

The tag is derived from the Linux version and both files in configs/. scripts/tag.sh prints it; changing an input creates a new tag without a manual version bump.

1. Push the kernel input changes. The Kernel GitHub Actions workflow builds the image on an arm64 runner and uploads an artifact named with the tag.
2. Run ./scripts/publish.sh after the workflow completes. The script downloads the artifact, verifies the kernel.org source checksum, and creates a GitHub release with the image, configuration, and corresponding source.
3. In the MSL checkout, pin the release with scripts/pin.sh kernel <tag> and commit the resulting changes.

scripts/publish.sh requires GitHub CLI (gh) authenticated with permission to create releases in onexay/msl-kernel. Set MSL_KERNEL_REPO to publish to another repository.

Contributing

Follow MSL's contribution guide. Sign off each commit with git commit -s under the Developer Certificate of Origin.

License

The build scripts and configuration are Apache-2.0; see LICENSE. The Linux kernel is GPL-2.0. Each published release includes the corresponding source.