Re: [PATCH 05/11] x86: remove HIGHMEM64G support

[Arnd Bergmann]

On Sat, Apr 12, 2025, at 01:44, Dave Hansen wrote:
> Has anyone run into any problems on 6.15-rc1 with this stuff?
>
> 0xf75fe000 is the mem_map[] entry for the first page >4GB. It obviously
> wasn't allocated, thus the oops. Looks like the memblock for the >4GB
> memory didn't get removed although the pgdats seem correct.
>
> I'll dig into it some more. Just wanted to make sure there wasn't a fix
> out there already.
>
> The way I'm triggering this is booting qemu with a 32-bit PAE kernel,
> and "-m 4096" (or more).

I have reproduced the bug now and found that it did not happen in
my series. Bisection points to Mike Rapoport's highmem series,
specifically  6faea3422e3b ("arch, mm: streamline HIGHMEM freeing")

There was a related bug that was caused by an earlier version
of my series when I also removed CONFIG_PHYS_ADDR_T_64BIT
https://lore.kernel.org/all/202412201005.77fb063-lkp@xxxxxxxxx/

    Arnd