大会说明找到多少线程在多核心系统启用 [英] Assembly instructions to find how many threads are enabled in a multi-core system

问题描述

我工作一个最基本的系统，我需要启动后的某个确定有多少核心和线程被启用，这样我就可以送他们SIPI事件上。我也希望每个线程知道它是哪个线程。

I'm working on a bare-bones system in which I need to determine sometime after boot how many cores and threads are enabled, so that I can send them SIPI events. I also want each thread to know which thread it is.

例如，在HT单核配置中启用，我们有（例如，英特尔凌动）：

For instance, in a single-core configuration with HT enabled, we have (for instance, Intel Atom):

thread 0 --> core 0 thread 0
thread 1 --> core 0 thread 1

虽然没有HT我们有一个双核的配置（例如，酷睿2）：

While in a dual-core configuration with no HT we have (for instance, Core 2 Duo):

thread 0 --> core 0 thread 0
thread 1 --> core 1 thread 0

什么是确定最好的方法？

What's the best way to determine this?

编辑：我发现每个线程如何能找到是哪个线程。我还没有找到如何确定多少个核心也有。

I found how each thread can find which thread it is. I still haven't found how to determine how many cores there are.

推荐答案

我研究了一下，这些事实走了过来。 CPUID 与 EAX = 01H 返回的APIC ID EBX [31:24] 和 EDX HT能[28] 。

I researched it a bit and came up with these facts. cpuid with eax = 01h returns the APIC ID in EBX[31:24] and HT enable in EDX[28].

这code应该做的工作：

This code should do the work:

    ; this code will put the thread id into ecx
    ; and the core id into ebx

    mov eax, 01h
    cpuid
    ; get APIC ID from EBX[31:24]
    shr ebx, 24
    and ebx, 0ffh; not really necessary but makes the code nice

    ; get HT enable bit from EDX[28]
    test edx, 010000000h
    jz ht_off

    ; HT is on
    ; bit 0 of EBX is the thread
    ; bits 7:1 are the core
    mov ecx, ebx
    and ecx, 01h
    shr ebx, 1

    jmp done

ht_off:
    ; the thread is always 0
    xor ecx, ecx

done:

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