linux-kernel - Re: [PATCH] i386: For debugging, make the initial page table setup less forgiving.

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Message-ID: <462F9665.1090602@zytor.com>
Date:	Wed, 25 Apr 2007 10:56:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Zachary Amsden <zach@...are.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i386: For debugging, make the initial page table setup
 less forgiving.

Eric W. Biederman wrote:
>> This patch only affects the initial page tables, which should have been
>> thrown out *way* long ago at this point.
> 
> Yes.  I noticed this was happening a few days ago.
> I must not have mentioned it loudly enough.

You mentioned the continued use of init_mm.  This is *very* different.

What we're seeing here is that ON PSE-CAPABLE HARDWARE, we continue to
not just use the init_mm page directory, but the actual page *tables*,
which should all have been replaced with PSE large pages to begin with.

Reusing the initial page tables on non-PSE-capable hardware *sort of*
makes sense, but his hardware should not fall in that category, I don't
think?  (Unless it's one of these machines that fall over if you map the
bottom 4 MB with PSE pages?)

	-hpa
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