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Subject: Re: [edk2-devel] MP Services Protocol : Support Hyper threading or not
To: devel@edk2.groups.io, tigerliu@zhaoxin.com
References: <03f9e675800143189bc59fab08865256@zhaoxin.com>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <581d5952-32b2-56e3-30d5-7f7f24039fa0@redhat.com>
Date: Mon, 22 Feb 2021 11:39:47 +0100
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On 02/22/21 08:08, Tiger Liu(BJ-RD) wrote:
> Dear All:
> I have a question about MP Services Protocol.
> Does it support Hyper-threading technology?
> 
> For example:
> A Quad-cores CPU(with HT feature support), actually it is equal to 8 logical cores.
> Take assumption 8 logical cores are all healthy and being enabled.
> 
> So:
> 
> 1.      Will EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors()return total 8 logical processor cores?
> 
> 2.      Will EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() make all 8 logical cores do some tasks simultaneously?

My understanding is "yes", to both questions. Most of the MP stuff deals
with "logical processors".


BTW, if you check the EFI_MP_SERVICES_GET_PROCESSOR_INFO prototype, it
outputs EFI_PROCESSOR_INFORMATION. The latter has the following fields:

  EFI_CPU_PHYSICAL_LOCATION      Location;
  EXTENDED_PROCESSOR_INFORMATION ExtendedInformation;

The former gives you a package/core/thread identification for a
particular processor number. The latter (optionally) provides a 6-level
description (package / module / tile / die / core / thread). In each
information structure, "logical thread" is the finest granularity
information.

hth
Laszlo