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Re: Instability / caching problems on Qube 2 - solved ?

To: Peter Horton <pdh@colonel-panic.org>
Subject: Re: Instability / caching problems on Qube 2 - solved ?
From: Dominic Sweetman <dom@mips.com>
Date: Mon, 15 Dec 2003 09:04:49 +0000
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
In-reply-to: <20031215083236.GA1164@skeleton-jack>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20031214162605.GA18357@skeleton-jack> <20031215022717.GA16560@linux-mips.org> <20031215083236.GA1164@skeleton-jack>
Sender: linux-mips-bounce@linux-mips.org
My prejudices are showing but...

o Shouldn't the kernel should have a zero-tolerance policy towards cache
  aliases?  That is, no D-cache alias should ever be permitted to
  happen, not even in data you reasonably hope might be read-only?
  
  Aliases only appeared by a kind of mistake when the R4000 was
  opportunistically repackaged without the secondary cache (the L2
  cache tags used to keep track of the virtually-indexed L1s, and you
  got an exception if you created an L1-alias).

  They really aren't a feature to be tolerated in the hope you can
  clean up before disaster strikes.

o And I could never get my brains round cache maintenance if I used
  the same word ("flush") both for invalidate and write-back.

--
Dominic Sweetman
MIPS Technologies.


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