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From: Rusty Russell <rusty@rustcorp.com.au>
To: Christoph Lameter <clameter@sgi.com>
Subject: Re: [patch 05/14] percpu: Use a Kconfig variable to configure arch specific percpu setup
Date: Wed, 28 Nov 2007 12:36:01 +1100
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       Andi Kleen <ak@suse.de>, Ben Elliston <bje@air.net.au>
References: <20071127001407.859743255@sgi.com> <200711271530.47696.rusty@rustcorp.com.au> <Pine.LNX.4.64.0711271013130.2310@schroedinger.engr.sgi.com>
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On Wednesday 28 November 2007 05:14:47 Christoph Lameter wrote:
> On Tue, 27 Nov 2007, Rusty Russell wrote:
> > Have you considered moving x86-64's setup_per_cpu_areas into generic
> > code? It's a bit messier because some archs might not have set up NUMA
> > stuff yet, but it's logically generic...
>
> Yes that will happen later. This is just the early cleanup work. I
> plan to generally bring the two x86 arches in line. The pda will be
> folded into the per cpu area and after that its easy to do.

Unfortunately, we tried to get rid of the x86-64 pda (like i386) but you lose 
the ability to use the stack protection config option.  That's because it 
assumes that gs:0x68 (or something) is the stack canary; we need a YA gcc 
change to make this gs:__builtin_stack_canary_off (where gcc can emit 
__builtin_stack_canary_off as a weak absolute symbol, so we can override it 
for the kernel.

Cheers,
Rusty.