Re: [PATCH v2] mm: Fix memblock_free_late() when using deferred struct page

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2026-02-18 at 10:05 +0200, Mike Rapoport wrote:
> Apparently we do miss some piece of the puzzle, otherwise you'd see no
> crashes :)
> 
> I think an easy and backportable fix would be to make
> efi_free_boot_services() an initcall, so that it will surely run after
> deferred pages are initialized.
> And since the boot services memory is not memblock_alloc()ed but rather
> memblock_reserve()ed, it should be freed with free_reserved_area().
> 
> With the symptom fixed, we can audit memblock_free_late() and
> free_reserved_area() callers and see how to make this all less messy and
> more robust.

I will play around. The biggest issue I see with this is that
efi_free_boot_services() also manipulates the efi memmap, and that's
done without any locking whatsoever.

I'm semi tempted to split that part. We can unmap the boot services
from EFI memory in the current spot, and defer the actual freeing.

Cheers,
Ben.