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From: ebiederm@xmission.com (Eric W. Biederman)
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Terence Ripperda <tripperda@nvidia.com>, linux-kernel@vger.kernel.org
Subject: Re: PAT support
Date: 14 Apr 2004 22:05:25 -0600	[thread overview]
Message-ID: <m1k70h6g3e.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <407B7BDE.5030002@colorfullife.com>

Manfred Spraul <manfred@colorfullife.com> writes:

> Hi Terence,
> 
> in your patch, you write
> +/* Here is the PAT's default layout on ia32 cpus when we are done.
> + * PAT0: Write Back
> + * PAT1: Write Combine
> + * PAT2: Uncached
> + * PAT3: Uncacheable
> + * PAT4: Write Through
> + * PAT5: Write Protect
> + * PAT6: Uncached
> + * PAT7: Uncacheable
> 
> Is that layout possible?
> There is an errata in the B2 and C1 stepping of the Pentium 4 cpus that results
> in incorrect PAT numbers: the highest bit is ignored by the CPU under some
> circumstances. There's a similar errata (E27) that affects all Pentium 3 cpus:
> The highest bit is always ignored.
> I think we need a fallback to 4 PAT entries.

Write Through and Write Protect are essentially useless.  So that should
be easy to do.

Eric

  parent reply	other threads:[~2004-04-15  4:05 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-04-13  5:34 Manfred Spraul
2004-04-13 14:02 ` Pavel Machek
2004-04-13 16:40 ` Terence Ripperda
2004-04-15  4:05 ` Eric W. Biederman [this message]
  -- strict thread matches above, loose matches on Subject: below --
2004-04-15 21:38 Albert Cahalan
     [not found] <1KifY-uA-7@gated-at.bofh.it>
2004-04-13  0:01 ` Andi Kleen
2004-04-13 16:21   ` Terence Ripperda
2004-04-14  0:58     ` Andi Kleen
2004-04-16 18:07       ` Terence Ripperda
2004-04-17  0:42         ` Andi Kleen
2004-04-19 22:54           ` Terence Ripperda
2004-04-20 18:51             ` Andi Kleen
2004-04-21 23:19               ` Terence Ripperda
2004-04-22  4:21                 ` Andi Kleen
2004-04-15  4:11   ` Eric W. Biederman
2004-04-15 16:38     ` Andi Kleen
2004-04-15 18:39       ` Eric W. Biederman
2004-04-12 22:29 Terence Ripperda
2004-04-13  8:36 ` Andy Whitcroft
2004-04-13 16:50   ` Terence Ripperda

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