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Re: Promblem with PREF (prefetching) in memcpy

To: Hartvig Ekner <hartvige@mips.com>
Subject: Re: Promblem with PREF (prefetching) in memcpy
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 4 Oct 2002 14:38:45 +0200
Cc: Dominic Sweetman <dom@algor.co.uk>, Carsten Langgaard <carstenl@mips.com>, linux-mips@linux-mips.org
In-reply-to: <200210041233.g94CXrQ29071@copfs01.mips.com>; from hartvige@mips.com on Fri, Oct 04, 2002 at 02:33:53PM +0200
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200210041153.MAA12052@mudchute.algor.co.uk> <200210041233.g94CXrQ29071@copfs01.mips.com>
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On Fri, Oct 04, 2002 at 02:33:53PM +0200, Hartvig Ekner wrote:

> this problem occurs in kernel space (kseg0), not user space. In user space
> there is no problem due to the TLB "protection" of PREFs going outside the
> process working set, but that doesn't help in kernel mode.

Assume a userspace device driver having some hardware mapped immediately
following a ordinary memory mapping.  In that case it would be possible
for prefetch to run from the one into the next mapping - boom.

  Ralf

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