setup_per_cpu_areas just prepare a per-cpu area for each
possible cpu, and it doesn't try to start up other possible cpu(s).

The address of  a per-cpu area corresponding to this cpu will be 
written to its per-cpu-area register , before starting up.

Starting up other non-boot cpu happens in start_secondary function.

Larry

------------------ Original ------------------
From:  "Dave Tian"<dave.jing.tian@gmail.com>;
Date:  Sat, Apr 23, 2016 10:02 PM
To:  "ÂäºÛ"<losemyheaven@qq.com>;
Cc:  "kernelnewbies"<kernelnewbies@kernelnewbies.org>;
Subject:  Re: where is __percpu_seg initialized?

load_percpu_segment, which is called by switch_to_new_gdt in setup_per_cpu_areas.

-daveti


> On Apr 23, 2016, at 3:24 AM, ÂäºÛ <losemyheaven@qq.com> wrote:
>
> Hi all:
> I knew the kernel implement the per-cpu variable via __percpu_seg. For example on x86 architecture, it's defined as:
>
> #ifdef CONFIG_X86_64
> #define __percpu_seg gs
> #define __percpu_mov_op movq
> #else
> #define __percpu_seg fs
> #define __percpu_mov_op movl
> #endif
>    
> But I'm curious where __percpu_seg is initialized?? I fail to find the relative code. Thanks.
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