linux-kernel - Re: [PATCH] x86: introduce a new Linux defined feature flag for PAT support

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Message-ID: <482262C7.9020307@keyaccess.nl>
Date:	Thu, 08 May 2008 04:17:43 +0200
From:	Rene Herman <rene.herman@...access.nl>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Adrian Bunk <bunk@...nel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	akpm@...ux-foundation.org, Pavel Machek <pavel@...e.cz>
Subject: Re: [PATCH] x86: introduce a new Linux defined feature flag for PAT
 support

On 08-05-08 04:11, H. Peter Anvin wrote:

> 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;

if (cpu_has_pat_good) would have been the exact same as now. Feel free
to drop the cpu_has_pat one but it's not crap. That whitelist thing
checks nothing -- and things like CONSTANT_TSC also don't, so I didn't
make the feature itself conditional. It has but one call site anyway.

Rene.
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