linux-kernel - Re: [tip:x86/pat] x86: Relegate CONFIG_PAT and CONFIG

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Date:	Mon, 12 Oct 2009 10:45:38 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, arjan@...radead.org, hmh@....eng.br,
	rdreier@...co.com, tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/pat] x86: Relegate CONFIG_PAT and CONFIG_MTRR configurability
 to EMBEDDED

H. Peter Anvin wrote:
> On 10/12/2009 04:10 AM, tip-bot for Arjan van de Ven wrote:
>> Commit-ID:  c03cb3149daed3e411657e3212d05ae27cf1a874
>> Gitweb:     http://git.kernel.org/tip/c03cb3149daed3e411657e3212d05ae27cf1a874
>> Author:     Arjan van de Ven <arjan@...radead.org>
>> AuthorDate: Sun, 11 Oct 2009 10:33:02 -0700
>> Committer:  Ingo Molnar <mingo@...e.hu>
>> CommitDate: Mon, 12 Oct 2009 13:06:57 +0200
>>
>> x86: Relegate CONFIG_PAT and CONFIG_MTRR configurability to EMBEDDED
>>
>> MTRR and PAT support (which got added to CPUs over 10 years ago)
>> are no longer really optional in that more and more things are
>> depending on PAT just working, including various drivers and newer
>> versions of X.  (to not even speak of MTRR)
>>
>> Having this as a regular config option just no longer makes sense.
>>
>> This patch relegates CONFIG_X86_PAT to the EMBEDDED category so
>> ultra-embedded can still disable it if they really need to.
>>
> 
> Should we combine this with removing the whitelist (which is largely
> vestigial at this point) and replace it with a blacklist (possibly
> empty)?  I still haven't seen any evidence that there are any CPUs which
> have problems, and PAT support go back all the way to Pentium III -- and
> page table attributes can be used all the way back to 386, it just
> excludes the WC type.

I would be in favor of that; other operating systems have been using pat everywhere
since the pII days anyway.
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