linux-kernel - Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

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Date:	Wed, 18 Jul 2007 13:33:29 -0400
From:	Phillip Susi <psusi@....rr.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Matt Mackall <mpm@...enic.com>,
	Rene Herman <rene.herman@...il.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Jesper Juhl <jesper.juhl@...il.com>,
	Ray Lee <ray-lk@...rabbit.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	William Lee Irwin III <wli@...omorphy.com>,
	David Chinner <dgc@....com>
Subject: Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

Alan Cox wrote:
>> Why do the two pages have to be physically contiguous?  The stack just 
>> needs to be two contiguous pages in virtual memory, but they can map to 
>> any two pages anywhere in physical memory.
> 
> Historically we allowed DMA off the stack on old x86 systems. Removing
> that while a good idea would take a lot of auditing. We also have a very
> limited vmalloc window for mapped pages and filling that with stacks
> would be bad.

Wow, DMA off the stack?  That's just crazy.

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