linux-kernel - Re: [PATCH 0/1] x86/cpu: don't allocate fpu->state for swapper/0

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Message-ID: <20150314111648.GD3114@pd.tnic>
Date:	Sat, 14 Mar 2015 12:16:48 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH 0/1] x86/cpu: don't allocate fpu->state for swapper/0

On Fri, Mar 13, 2015 at 07:26:56PM +0100, Oleg Nesterov wrote:
> Hello.
> 
> This patch is "out of order" a bit, but since Borislav mentioned this
> during review...
> 
> And I was going to send the 2nd one (below), but it turns out that
> __init_refok is not discarded? So is there any way to do
> 
> 	void __init init_function();
> 
> 	void non_init_func()
> 	{
> 		if (can_only_be_true_before_free_initmem)
> 			init_function();
> 	}
> 
> and avoid the warning?

Actually, I was wondering if we could be even more radical and do
the boot cpu-specific stuff only in the BSP boot path. For example,
somewhere down that path:

start_kernel
|-> check_bugs
   |-> check_fpu		--- btw, we do FPU stuff here already too
   |-> xstate_enable_boot_cpu

instead of this state machine with function pointers hackery.

I'll try to play with this and see whether something breaks.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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