linux-kernel - Re: [PATCH 00 of 10] x86: unify asm/pgtable.h

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Message-ID: <478405DA.40303@goop.org>
Date:	Tue, 08 Jan 2008 15:23:06 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	LKML <linux-kernel@...r.kernel.org>, Andi Kleen <ak@...e.de>,
	Glauber de Oliveira Costa <glommer@...il.com>,
	Jan Beulich <jbeulich@...ell.com>
Subject: Re: [PATCH 00 of 10] x86: unify asm/pgtable.h

Ingo Molnar wrote:
> threw this into the random test setup: it found the attached config 
> after a few iterations, which needed the fix below. (config builds and 
> boots fine with this fix)
>
> the problem was that set_pud() is used by 
> include/asm-generic/pgtable-nopud.h, to build set_pgd():
>
> #define set_pgd(pgdptr, pgdval)                 set_pud((pud_t *)(pgdptr), (pud_t) { pgdval })
>   

Oh, yeah.  That's bitten me before, but I guess I lost that part of the 
patch somewhere :(.

> it's truly a maze ... took me 10 straight minutes of staring at the code 
> to figure out where the set_pud() came from :-/
>   

It's pretty awful.  The pagetable level folding stuff is fairly deep 
into "too clever" territory, but its hard to see what better 
alternatives there are...  Dropping non-PAE support would be nice, but 
impractical given that even relatively recent chips are missing support 
for it.

> anyway, your patchset is holding up pretty good so far in testing.
>   

Great!

    J
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