CachyOS Kernel Workflow

This repo builds stock-Arch-installable kernel packages from the upstream CachyOS sources.

The point is narrow:

• keep the CachyOS bore kernel tuning
• keep the Clang ThinLTO path
• target generic_v3 inside the kernel config so a GitHub runner does not accidentally build for its own CPU
• emit normal x86_64 Arch packages so stock pacman accepts them
• give you a patch queue for small hardware-specific fixes

This exists because the prebuilt CachyOS x86_64_v3 packages are rejected by stock Arch pacman with package architecture is not valid.

What The Workflow Builds

Default output:

• linux-cachyos-bore-lto
• linux-cachyos-bore-lto-headers

Current scope:

• bore
• Clang
• ThinLTO
• generic_v3

Not enabled by default:

• AutoFDO
• Propeller

Upstream ships these only on the default linux-cachyos package (EEVDF), not on linux-cachyos-bore. They need a profile file from a two-pass build (build, profile a real workload with perf record, rebuild with the profile), and that profile is CPU-specific. A profile captured on a GitHub Actions runner would be tuned to the runner's CPU, not yours, so the payoff is thin.

Upstream base:

• repository: https://github.com/CachyOS/linux-cachyos
• package directory: linux-cachyos-bore
• scheduler: bore
• LLVM LTO mode: thin

Why This Repo Forces generic_v3

Upstream CachyOS exposes _processor_opt, and the PKGBUILD defaults to native when it is left empty. On GitHub Actions that would optimize the kernel for the runner CPU instead of a portable x86-64-v3 target.

This repo sets:

• _processor_opt=generic_v3
• _use_llvm_lto=thin
• _use_lto_suffix=yes
• _cc_harder=yes

It also unsets CI and GITHUB_RUN_ID before makepkg, because the upstream PKGBUILD detects CI and otherwise flips the kernel from -O3 to -Os.

Use patches/*.patch only for concrete issues you can name.

Layout

• config/build.env
• scripts/build-kernel.sh
• patches/README.md
• .github/workflows/build.yml

Usage

Run the Build CachyOS Kernel workflow from the Actions tab (manual workflow_dispatch), or run it on the 0 0 */5 * * schedule (every 5 days at midnight UTC). Manual runs let you override upstream_ref and processor_opt. Scheduled runs build whatever upstream master points at.

The workflow uploads package artifacts from out/ as GitHub Actions artifacts.

On your Arch system, install the resulting packages with:

sudo pacman -U ./linux-cachyos-bore-lto-*.pkg.tar.zst ./linux-cachyos-bore-lto-headers-*.pkg.tar.zst

Then regenerate boot entries if needed:

sudo grub-mkconfig -o /boot/grub/grub.cfg

Scheduled Builds And Upstream Sync

On the 5-day schedule, check-upstream compares CachyOS's linux-cachyos HEAD against the hash on the tracking branch and skips the build if they match. After a successful build, two steps run:

• Sync upstream bore dir mirrors linux-cachyos-bore/ into upstream/linux-cachyos-bore/ on master.
• Update tracking branch records the built hash on tracking for the next comparison.

Both are skipped on manual workflow_dispatch runs.

Sources

• CachyOS kernel repo: https://github.com/CachyOS/linux-cachyos
• CachyOS kernel wiki: https://wiki.cachyos.org/features/kernel