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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: Carsten Langgaard <>
Date: Thu, 09 Jan 2003 21:10:01 +0100
Cc: Mike Uhler <>, "Maciej W. Rozycki" <>, Dominic Sweetman <>,
Original-recipient: rfc822;
References: <> <> <>
Ralf Baechle wrote:

> On Wed, Jan 08, 2003 at 11:33:01AM -0800, Mike Uhler wrote:
> > >  They do are different: KSEG0+entry*0x2000, likewise for XKPHYS -- see the
> > > patch.
> >
> > This is precisely what we use for our internal testing (which is also
> > exported to MIPS32 and MIPS64 architecture licensees) to initialize the
> > TLB.  I have not yet seen a case where this fails, and would be interested
> > in hearing about any case where it does fail.
> 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.

All MIPS's CPUs need these unique TLB entries otherwise you get a machine check
Inspired by Kevin Kissell's changes to openBSD, I made the above change
(KSEG0+entry*0x2000) to the TLB routine in linux. It was done when we first 
to boot linux on the MIPS 4Kc CPU, a couple of years ago.

>   Ralf

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