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Date: Wed, 1 Oct 2003 10:00:33 +0200
From: Andi Kleen <ak@suse.de>
To: Jamie Lokier <jamie@shareable.org>
Cc: Andi Kleen <ak@suse.de>, akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Mutilated form of Andi Kleen's AMD prefetch errata patch
Message-ID: <20031001080033.GP15853@wotan.suse.de>
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On Wed, Oct 01, 2003 at 08:55:51AM +0100, Jamie Lokier wrote:
> Andi Kleen wrote:
> > Jamie Lokier <jamie@shareable.org> writes:
> > > It is easy enough to fix by making the fault handler not take
> > > mmap_sem if the fault's in the kernel address range.  (With apologies
> > > to the folk running kernel mode userspace...)
> > 
> > It won't work because kernel can cause user space faults
> > (think get_user). And handling these must be protected.
> 
> Are we mis-communicating?  By "fault in the kernel address range", I

Yep, we were. I read it as "instruction faulting is in kernel range"
(aka you check the ring0 bit in the error_code), not checking cr2 >= TASK_SIZE.

-Andi