Three improvements derived from running CachyOS 2026-06-28 in QEMU
and comparing to the Red Bear OS boot sequence.
drivers/pcid/src/main.rs:
- PIIX4/PIIX5 IDE (vendor 0x8086, device 0x7010/0x7111) gets a
'fixed BAR' quirk that pins BAR0..3 to the legacy IDE IO ports
(0x1F0/0x3F6/0x170/0x376) and BAR4 to the BM-DMA window
(0xC0C0/0xC0C8). The standard QEMU firmware model ignores BAR
programming and uses the legacy IO layout directly; without the
fix the ided driver reads whatever happens to be in config space
and misses the bus-master window. Linux applies the same quirk in
drivers/ata/ata_piix.c.
- Class 0x03 (display controller) devices now log a vgaarb-style
'setting as boot VGA device' message. On QEMU there's only the
Bochs 1234:1111, so the arbitration is unambiguous; on real
multi-GPU hardware the message makes the kernel's choice
observable. Full scheme-level arbitration (a /scheme/system/vga
returning the owner) is left for a future change.
initfs/tools/Cargo.toml + initfs/tools/src/bin/loop_mnt.rs:
- New loop_mnt binary that scans /scheme/initfs/etc/* for block
devices and probes each for the RedoxFS magic. On the first match
it writes the path to /scheme/runtime/loop_mnt_target, so that
50_rootfs.service / redoxfs can read the choice and fall back to
the dynamic-discovery path that CachyOS's archiso_loop_mnt hook
provides. The implementation is intentionally a no-op when no
RedoxFS volume is found, so the explicit initfs.toml path remains
the source of truth on a normal boot.
init.initfs.d/45_loop_mnt.service:
- Init service unit that invokes loop_mnt after pcid-spawner-initfs
but with weak ordering so it never blocks the existing 50_rootfs
path. Mirrors the CachyOS archiso_loop_mnt role without
conflicting with the explicit initfs.toml flow.
recipes/core/base-initfs/recipe.toml:
- Cross-compile loop_mnt during the base-initfs build so the binary
is present in the packed initfs image, and place it before the
redox-initfs-ar archive step so the service file is included in
the same image.
Red Bear OS