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Date: Wed, 07 May 2008 19:11:23 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Rene Herman <rene.herman@keyaccess.nl>,
       Thomas Gleixner <tglx@linutronix.de>, Adrian Bunk <bunk@kernel.org>,
       Yinghai Lu <yhlu.kernel@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       Linux Kernel <linux-kernel@vger.kernel.org>, akpm@linux-foundation.org,
       Pavel Machek <pavel@suse.cz>
Subject: Re: [PATCH] x86: introduce a new Linux defined feature flag for PAT
 support
References: <48210A71.1060409@keyaccess.nl> <86802c440805061939q39ff5500h3c9e229ecbc6b2e6@mail.gmail.com> <20080507124650.GD29935@cs181133002.pp.htv.fi> <alpine.LFD.1.10.0805072122270.3318@apollo.tec.linutronix.de> <48221AE3.6020602@keyaccess.nl> <482233F0.7040000@zytor.com> <48224318.8020209@keyaccess.nl> <48224361.5080102@zytor.com> <48224507.8010102@keyaccess.nl> <alpine.LFD.1.10.0805071716060.3024@woody.linux-foundation.org> <48224930.9030901@keyaccess.nl> <48225DEC.2030502@keyaccess.nl> <alpine.LFD.1.10.0805071857430.3024@woody.linux-foundation.org>
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Linus Torvalds wrote:
> 
> On Thu, 8 May 2008, Rene Herman wrote:
>> Okay, so how's this? Seem to work well for me and makes me happy. Only
>> tested on UP.
> 
> Looks sane to me.
> 
> Not that I ever really saw the point about this whole argument in the 
> first place. Clearing the flags wasn't really wrong to begin with.
> 

Indeed it wasn't, and at least I have no interest of maintaining what is 
in effect an in-kernel version of x86info(1).

*Certainly* I don't want anything like this crap:

> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 277446c..6ee3efb 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -43,7 +43,7 @@ static int pat_known_cpu(void)
>     if (!pat_wc_enabled)
>         return 0;
> 
> -    if (cpu_has_pat)
> +    if (cpu_has_pat && cpu_has_pat_good)
>         return 1;
> 
>     pat_wc_enabled = 0; 

	-hpa