[edk2-devel] MP Services Protocol : Support Hyper threading or not

[Laszlo Ersek]

On 02/23/21 02:17, fanjianfeng at byosoft.com.cn wrote:
> " Will EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() make all 8 logical cores do some tasks simultaneously?"
> 
> All APs logical processors excute AP task, not including BSP. Acutally the answer is 7.

Good point :)

Thanks
Laszlo

> 
> Jeff
>  
> From: Laszlo Ersek
> Date: 2021-02-22 18:39
> To: devel; tigerliu
> Subject: Re: [edk2-devel] MP Services Protocol : Support Hyper threading or not
> 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
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