Re: [PATCH 4/5] x86-64: Remove the PDA

From: Tejun Heo
Date: Sun Jan 18 2009 - 22:05:59 EST

Hello, Brian.

Brian Gerst wrote:
>> As discussed before, the above chunks do drop one #ifdef CONFIG_SMP
>> but it does add a obscure relocation and please note that it's
>> different from early_gdt_descr. early_gdt_descr is needed to bring up
>> the cpu so there's no other way to do it but to relocate it in
>> assembly. If you absolutely have to relocate irq_stack_ptr early,
>> please do it in C code in head64.c but then again irq_stack_ptr is not
>> even necessary till traps_init() which is way after per cpu area
>> setup. So, the above two chunks are not necessary && even if they go
>> in, they don't have much to do with this patch.
> I'll give you that this particular variable doesn't need early
> adjustment currently. I'd prefer if you left the ifdef off the first
> hunk, though. A comment will suffice to document that the initial
> value is going to be overwritten later on SMP.

Yeah, maybe. I don't know. If we ever get to a point where we can
fully initialize per cpu area for cpu0, things like this can probably
go away, but for now, I just thought it would be better to make it
clear that UP and SMP are taking different initialization paths &&
that was how the code looked like before this patch, so... But no big
deal one way or another, right?


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