linux-kernel - Re: [PATCH 2/5] x86: PAT: fix ambiguous paranoia check in pat

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Message-ID: <4850A6DD.8070903@keyaccess.nl>
Date:	Thu, 12 Jun 2008 06:32:29 +0200
From:	Rene Herman <rene.herman@...access.nl>
To:	Andreas Herrmann <andreas.herrmann3@....com>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Suresh B Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH 2/5] x86: PAT: fix ambiguous paranoia check in pat_init()

On 11-06-08 18:12, Andreas Herrmann wrote:

>> Again not wrong, or at least by design. Thomas Gleixner did it this way and 
>> with that "paranoia check" explicitly bombing out only for SMP this 
>> wouldn't have been by accident. He no doubt knows why he did so (and he's 
>> in CC so if we're real lucky we might also now...)
> 
> I guess at the time Thomas' patch was commited this was just fine.
> 
> But with the recent Transmeta/Centaur patch, validate_pat_support()
> returns w/o disabling PAT even for such vendor's CPUs that don't
> support PAT,

In a sense that recent patch in the x86 tree could be consired the buggy 
one as it fails to explicitly whitelist those models with functional PAT 
while THAT was the setup of things here -- but yes, don't get me wrong, 
I also think that setup wasn't particularly great.

Your followup patch turns the whitelist into a blacklist, blacklisting 
those Intel models which weren't specifically whitelisted before, which 
is a saner approach, so <shrug>. If things are ready for that, all the 
better.

Rene.
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