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Re: [patch] MIPS64 R4k TLB refill CP0 hazards

To: Ralf Baechle <ralf@oss.sgi.com>
Subject: Re: [patch] MIPS64 R4k TLB refill CP0 hazards
From: Carsten Langgaard <carstenl@mips.com>
Date: Fri, 02 Aug 2002 11:32:18 +0200
Cc: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, linux-mips@fnet.fr, linux-mips@oss.sgi.com
References: <20020731223158.A6394@dea.linux-mips.net> <Pine.GSO.3.96.1020801171104.8256E-100000@delta.ds2.pg.gda.pl> <20020801191804.D22824@dea.linux-mips.net>
Sender: owner-linux-mips@oss.sgi.com
Ralf Baechle wrote:

> On Thu, Aug 01, 2002 at 05:24:43PM +0200, Maciej W. Rozycki wrote:
>
> >  After looking at the generated assembly I discovered the handlers don't
> > fit in 128 bytes.  They didn't crash since I have modules disabled for
> > now, so the vmalloc path didn't get hit and the user path happened to fit,
> > but it was pure luck.  The path got hit before I fixed a bug in gas though
> > -- that's the explanation of the false cache error exceptions I used to
> > observe.
>
> Ouch.  It was a known problem but we simply ignored it for a while as that
> handler just overwrites the cache error handler which normally should be
> used extremly rarely, if at all.  The problem is somewhat itching by now
> as we're supporting the SB1 core which in it's revision one may throw
> spurious cache errors, so the handler is actually used ...
>

Maybe it's time for some intelligent check for the size of these exception
routine.

/Carsten



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