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

[Arnd Bergmann]

On Sat, Apr 12, 2025, at 12:05, Mike Rapoport wrote:
> On Fri, Apr 11, 2025 at 04:44:13PM -0700, 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.
>
> That's apparently because of 6faea3422e3b ("arch, mm: streamline HIGHMEM
> freeing"). 
> Freeing of high memory was clamped to the end of ZONE_HIGHMEM which is 4G
> and after 6faea3422e3b there's no more clamping, so memblock_free_all()
> tries to free memory >4G as well.

Ah, I should have waited with my bisection, you found it first...

>> I'll dig into it some more. Just wanted to make sure there wasn't a fix
>> out there already.
>
> This should fix it.

Confirmed on 6.15-rc1.

     Arnd