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A yuka.dev report describes booting Linux to a shell on an M4 Mac mini after working around locked hardware registers and early-boot issues. The developer then encountered a crash involving the CPU’s WFI instruction; the supplied account ends before explaining the full diagnosis or fix.
A developer writing at yuka.dev has documented getting Linux to a shell on an Apple M4 Mac mini, after adapting the boot process around M4-specific hardware behavior and debugging several early kernel failures. The account also describes a later crash associated with the WFI instruction, but the supplied report excerpt ends before giving the final diagnosis or outcome of that issue.
The developer bought the M4 Mac mini in November 2024, expecting it might be supported along lines similar to earlier Apple Silicon systems. Work was complicated by the M4 generation’s requirement for SPTM, or Secure Page Table Monitor, which the report says hardens macOS’s kernel. Earlier Linux bring-up work often relied on tracing macOS hardware interactions through the m1n1 hypervisor; supporting that approach on M4 required significant changes to m1n1. The author described those changes as beyond their experience at the time.
Initial experiments instead focused on booting Linux directly. The developer installed m1n1 as a custom boot object and used a serial console to inspect startup. Two register operations caused crashes: initializing GXF functionality, which the report says is disabled or locked in raw boot mode on M4-and-newer systems, and writing the per-core Reset Vector Base Address Register (RVBAR). The author found that skipping GXF initialization and the RVBAR write allowed m1n1 to proceed further; the report notes the RVBAR already held the needed value.
Later, a minimal device tree and small assembly-based print test helped locate another failure. Once Linux enabled its memory-management unit, the debug UART stopped working because the initial page tables did not map its memory-mapped I/O address. Adding an identity mapping restored output further into boot. The developer then traced a crash to a write to SYS_IMP_APL_VM_TMR_FIQ_ENA_EL2, a virtualization-related CPU register. Commenting out that write allowed the kernel to reach a shell. The author says newer iBoot versions have since unlocked the register, making that workaround unnecessary.
What the M4 Bring-Up Shows
The report offers a practical account of the obstacles involved in bringing mainline Linux to newer Apple Silicon, rather than evidence of a finished, broadly usable Linux installation for M4 Macs. Reaching a shell shows that a Linux kernel can execute on the Mac mini with the described boot setup, while the register and device-tree problems illustrate how platform-specific details can stop a system long before users reach a desktop.
The work also matters to developers because the M4’s SPTM requirement complicates the hypervisor-based tracing method used in earlier efforts. That can make it harder to learn how macOS configures undocumented hardware. The account credits the Asahi Linux team’s prior work, but it does not establish that the M4 is fully supported by Asahi Linux or that ordinary users can install and run it reliably.
serial console adapter for Mac mini
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From Boot Experiments to Kernel Output
The developer’s experiments began after purchasing the Mac mini in November 2024. A brief progress note dated December 1, 2024, reported that the setup exposed a USB proxy and allowed a shell through m1n1’s UART proxy. That was an early debugging milestone, not a report of Linux reaching a normal user environment.
After a period without work on the machine, the author resumed experiments around the end of 2025. A minimal device tree included the CPU cores and Apple’s AIC interrupt controller. Linux initially produced no useful serial output, so the author inserted a one-character print routine and narrowed down where output stopped. On January 23, 2026, the author reported getting early kernel messages after setting an early console parameter and adding the missing stdout-path entry to the device tree. That made register dumps and stack traces available for further debugging.
“After I commented out this write, the kernel booted to a shell.”
— The developer, in the yuka.dev report
USB to serial converter for Linux debugging
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The WFI Crash Remains Open
The supplied report material ends as the developer describes a crash during attempts to start secondary CPU cores. The account says earlier Apple Silicon CPUs had known quirks involving the WFI instruction, which allows a core to wait for an event, and mentions an XNU open-source code setting named ARM64_REG_CYC_OVRD_ok2pwrdn_force_mask. But the excerpt stops before stating exactly how that setting affected the M4, what triggered the crash, or whether the developer resolved it.
It is also unclear from the material provided whether the boot-to-shell result was repeatable across restarts, which hardware components worked, or how much of the system was usable beyond the shell. No release status, installation guide for general users, or formal M4 support announcement is included. The findings are the author’s technical account, not an independent compatibility assessment.
ARM development board with serial port
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Further Testing Needed on M4
The next step is to establish whether the secondary-core issue can be diagnosed and addressed, then document which M4 features work in a sustained Linux session. The report’s account of missing console mappings, locked registers and CPU-specific behavior suggests that more kernel and bootloader changes may be needed before the result can be treated as dependable support.
Readers seeking updates should consult the developer’s full yuka.dev post and ongoing Asahi Linux project work. The available material does not state a release date or promise of general M4 support, so neither should be assumed from this successful shell boot alone.
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Key Questions
Did Linux boot on the M4 Mac mini?
According to the developer’s yuka.dev account, the kernel eventually booted to a shell after several debugging changes. The report excerpt does not establish full hardware support or a ready-to-use installation.
What caused the early boot failures?
The author describes several separate issues: GXF initialization and an RVBAR write that caused crashes, an unmapped UART address after the MMU was enabled, and a write to a virtualization-related CPU register. Skipping or correcting those steps let boot progress further.
What does the report say about the WFI instruction?
It links a later crash during secondary-core startup to investigation of WFI-related CPU behavior. The supplied excerpt does not include the complete explanation or say whether the issue was fixed.
Does this mean Asahi Linux supports M4 Macs?
No such support announcement appears in the supplied material. One developer’s successful boot to a shell is a technical milestone, but it does not by itself show that M4 support is complete, stable or available to general users.
Source: hn
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