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

To: "Maciej W. Rozycki" <>
Subject: Re: [patch] Use XKPHYS for 64-bit TLB flushes
From: Ralf Baechle <>
Date: Thu, 9 Jan 2003 02:36:01 +0100
Cc: Mike Uhler <>, Dominic Sweetman <>,
In-reply-to: <>; from on Wed, Jan 08, 2003 at 09:12:03PM +0100
Original-recipient: rfc822;
References: <> <>
User-agent: Mutt/
On Wed, Jan 08, 2003 at 09:12:03PM +0100, Maciej W. Rozycki wrote:

>  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?). 

I'm told the TLB Shutdown bit in the R4000 is basically implemented as an
overcurrent protection.  That is on many chips even a hit on several
entries won't cause a tlb shutdown until the matches do result in the
TLB drawing more than a certain current.

A tlbp on a KSEG0 address shouldn't happen.  If it's attempted we already
have worse problems.


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