Kernel panic on import when using kernel with CONFIG_X86_NATIVE_CPU on Zen4

[manschwetus]

System information

Type	Version/Name
Distribution Name	Gentoo Amd64
Distribution Version	---
Kernel Version	6.16.9 + 6.17.[8,10]
Architecture	X86_64
OpenZFS Version	2.3.[4,5]

Describe the problem you're observing

Kernel panic during early boot on rpool import

Describe how to reproduce the problem

Boot system with kernel build with CONFIG_X86_NATIVE_CPU=y, system boots flawless when kernel is buil with CONFIG_X86_NATIVE_CPU not set. Likely all 6.16 and 6.17 kernel versions are affected.

Include any warning/errors/backtraces from the system logs

none as panic during initrd, but mostly due to null pointer below zio_data_buf_free, around abd_iterate_func2 or abd_iterate_page_func

[manschwetus]

Interesting remark I have two Zen5 systems (P16s gen4 HX pro 370) which work fine with 6.17.10 and CONFIG_X86_NATIVE_CPU=y with zfs root using zfs 2.3.5

[robn]

@manschwetus could you get a screenshot of the panic? It'd be really useful!

What compiler & toolchain versions are being used here. Are they different on the Zen5 systems?

CONFIG_X86_NATIVE_CPU is only used to set compiler args in the kernel:

ifdef CONFIG_X86_NATIVE_CPU
        KBUILD_CFLAGS += -march=native
else
        KBUILD_CFLAGS += -march=x86-64 -mtune=generic
endif

So it'll be some subtle codegen thing of course. I wonder what the practical difference is between Zen 4 & 5 wrt to codegen, and if we're doing overriding something in a very weird way?

If we can get the trace, next step might be to disassemble some code.

[manschwetus]

Need to check but the systems are very similar.
Both use

• x86_64-pc-linux-gnu-14 => 14.3.1_p20250801
• coreutils 9.8-r1
• binutils x86_64-pc-linux-gnu-2.45

[manschwetus]

I made some video recordings, here some screen shots

I'll look if I have more, otherwise on next chance I'll retry and make sure to document if problem is still reproducible.