Re: [RFC 2/2] efi/memattr: add efi_mem_attr_table as a reserved region in 820_table_firmware

[Usama Arif]

On 10/01/2025 02:50, Dave Young wrote:
> Hi Usama,
> 
> On Thu, 9 Jan 2025 at 06:00, Usama Arif <usamaarif642@xxxxxxxxx> wrote:
>>
>> When this area is not reserved, it comes up as usable in
>> /sys/firmware/memmap. This means that kexec, which uses that memmap
>> to find usable memory regions, can select the region where
>> efi_mem_attr_table is and overwrite it and relocate_kernel.
> 
> Is the attr table BOOT SERVICE DATA?  If so, does efi_mem_reserve()
> work for you?
> Just refer to esrt.c.
> 

Hi Dave,

Its a bit difficult to reproduce the problem and therefore test the fix, but
we are seeing it a lot in production. Ard proposed the same thing in 
https://lore.kernel.org/all/6b4780a5-ada0-405e-9f0a-4d2186177f29@xxxxxxxxx/
but as I mentioned there, I dont think that efi_mem_reserve would help,
as efi_mem_reserve changes e820_table, while kexec looks at
/sys/firmware/memmap which uses e820_table_firmware.

Thanks,
Usama

> Thanks
> Dave
>