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From: "Albert D. Cahalan" <acahalan@cs.uml.edu>
Message-Id: <200103290610.f2T6A7s282810@saturn.cs.uml.edu>
Subject: Re: [patch] pae-2.4.3-C3
To: mingo@elte.hu
Date: Thu, 29 Mar 2001 01:10:07 -0500 (EST)
Cc: linux-kernel@vger.kernel.org (Linux Kernel List), linux-mm@kvack.org
In-Reply-To: <Pine.LNX.4.30.0103281151020.3657-200000@elte.hu> from "Ingo Molnar" at Mar 28, 2001 11:57:52 AM
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Ingo Molnar writes:

> the attached pae-2.4.3-C3 patch fixes the PAE code to work with SLAB
> FORCED_DEBUG (which enables redzoning) too.
> 
> the problem is that redzoning is enabled unconditionally, and SLAB has no
> information about how crutial alignment is in the case of any particular
> SLAB cache. The CPU generates a general protection fault if in PAE mode a
> non-16-byte aligned pgd is loaded into %cr3.

How about just fixing the debug code to align things? Sure it wastes
a bit of memory, but debug code is like that.

Sane alignment might be: largest power-of-two factor of the size,
or 4 bytes, which ever is larger. (adjust "4" per-arch as needed)
For an SMP config, set a minimum alignment equal to the cache line size.
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