Re: [PATCH v2] x86/efi: defer freeing of boot services memory

Ard Biesheuvel
2026-03-05T11:11:34Z

On Wed, 25 Feb 2026, at 07:55, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> efi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE
> and EFI_BOOT_SERVICES_DATA using memblock_free_late().
>
> There are two issue with that: memblock_free_late() should be used for
> memory allocated with memblock_alloc() while the memory reserved with
> memblock_reserve() should be freed with free_reserved_area().
>
> More acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
> efi_free_boot_services() is called before deferred initialization of the
> memory map is complete.
>
> Benjamin Herrenschmidt reports that this causes a leak of ~140MB of
> RAM on EC2 t3a.nano instances which only have 512MB or RAM.
>

Putting a fixes tag referencing a patch that dates back to 2011 doesn't seem that useful here. Is this really an issue that goes all the way back? Or did a later change trigger the actual leak?