From: Pavel Machek <pavel@suse.cz>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Terence Ripperda <tripperda@nvidia.com>, linux-kernel@vger.kernel.org
Subject: Re: PAT support
Date: Tue, 13 Apr 2004 16:02:53 +0200 [thread overview]
Message-ID: <20040413140253.GG468@openzaurus.ucw.cz> (raw)
In-Reply-To: <407B7BDE.5030002@colorfullife.com>
Hi!
> 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.
What about arranging it so that foo is always more restrictive than
foo|4? That way you can get some slowdowns on bad cpus, but it
will always be correct.
--
64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms
next prev parent reply other threads:[~2004-04-13 20:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-04-13 5:34 PAT support Manfred Spraul
2004-04-13 14:02 ` Pavel Machek [this message]
2004-04-13 16:40 ` Terence Ripperda
2004-04-15 4:05 ` Eric W. Biederman
-- 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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