linux-kernel - Re: [RFC 00/15] x86_64: Optimize percpu accesses

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Message-ID: <4875231F.1020506@zytor.com>
Date:	Wed, 09 Jul 2008 16:44:15 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

Arjan van de Ven wrote:
> On Wed, 09 Jul 2008 13:11:03 -0700
> Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> 
>> Ingo Molnar wrote:
>>> Note that the zero-based percpu problems are completely unrelated
>>> to stackprotector. I was able to hit them with a
>>> stackprotector-disabled gcc-4.2.3 environment.
>> The only reason we need to keep a zero-based pda is to support 
>> stack-protector.  If we drop drop it, we can drop the pda - and its 
>> special zero-based properties - entirely.
> 
> what's wrong with zero based btw?
> 

Two problems:

1. it means pda references are invalid if their offsets are ever more 
than CONFIG_PHYSICAL_BASE (which I do not think is likely, but still...)

2. some vague hints of a linker bug.

	-hpa
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