linux-kernel - Re: RFD: Does CONFIG_X86_LOCAL

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Message-ID: <20131011062002.GC4975@gmail.com>
Date:	Fri, 11 Oct 2013 08:20:02 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: RFD: Does CONFIG_X86_LOCAL_APIC still make sense?


* H. Peter Anvin <hpa@...or.com> wrote:

> I'm trying to wrap my head around if there are use cases where disabling 
> either CONFIG_X86_UP_APIC or CONFIG_X86_LOCAL_APIC would ever make sense 
> anymore.
> 
> I am guessing there are probably some small number of embedded systems 
> which still don't have LAPICs, but is it a significant number and does 
> anyone care for new kernels?  We are not talking about discontinuing 
> support for non-APIC configurations, just the configuration option.

I guess it depends on the kernel size difference. If it's more than just a 
few K then a patch will creep back via some CONFIG_EXPERT "reduce kernel 
bloat" route.

The thing is, if we allow non-apic configurations then we have paid most 
of the modularization, #ifdef and general maintenance price already. 
Adding a Kconfig just makes it more testable and breakages more apparent.

Unless I missed some aspects of this that would allow us to simplify code 
significantly that is.

Thanks,

	Ingo
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