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Re: [patch] Use XKPHYS for 64-bit TLB flushes

To: Ralf Baechle <>
Subject: Re: [patch] Use XKPHYS for 64-bit TLB flushes
From: "Maciej W. Rozycki" <>
Date: Wed, 8 Jan 2003 21:12:03 +0100 (MET)
Cc: Mike Uhler <>, Dominic Sweetman <>,
In-reply-to: <>
Organization: Technical University of Gdansk
Original-recipient: rfc822;
On Wed, 8 Jan 2003, Ralf Baechle wrote:

> We used to use just KSEG0 instead of KSEG0+entry*0x2000.  That was running
> fine over years but had to be changed for the sake of two CPUs afair.  There
> was some discussion on this list about this and I accepted the change by that
> time because Kevin imho correctly argued that the spec left it unspecified
> if an implementation is feeding addresses in an unmapped address space
> though the TLB.

 Well, like it or not, CAMs do not like multiple matches -- up to a
physical damage even.  So they should be avoided if possible.  While KSEG0
won't match for any real address translation, there is a non-zero
probability of executing a tlbp for it as a result of buggy code or
execution gone wild (root running crashme?). 

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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