Hi Pedro,

Yes, it is for  some specific test tools.

There are different performance between CPU cores, and the big cores are better than small cores.

Some legacy tools are executing with the highest performance CPU cores, In early CPU design, it is usually the first one.

We have to put them at the front of all CPU cores, otherwise some tests cannot pass.

Due to avoid this happened, we need to ensure CPU cores are ordered by big core first.

Best regards

Jack

From: Pedro Falcato <pedro.falcato@gmail.com>
Sent: Thursday, November 17, 2022 10:09 PM
To: devel@edk2.groups.io; Lin, JackX <jackx.lin@intel.com>
Cc: Chiu, Chasel <chasel.chiu@intel.com>; Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>; Oram, Isaac W <isaac.w.oram@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Dong, Eric <eric.dong@intel.com>; Kuo, Donald <donald.kuo@intel.com>; Kumar, Chandana C <chandana.c.kumar@intel.com>
Subject: Re: [edk2-devel] [edk2-platforms: PATCH] BIOS needs to present cores in order of relative performance in MADT

On Thu, Nov 17, 2022 at 6:01 AM JackX Lin <JackX.Lin@intel.com> wrote:

BIOS should keep MADT ordering by big core first then small core

Hi Jack,

Can you please elaborate why this is required? AFAIK nowhere in the ACPI spec does it say you need to order by big-little cores.

Is this some sort of regression for a specific OS? A useful commit message and/or some comments would be really useful here for posterity. 

Thanks,

Pedro Falcato