linux-kernel - Re: [PATCH 5/6] x86: move mtrr cpu cap setting early in early_init

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Message-ID: <86802c440809041217p454c4471y66a8ed6907d9cc8@mail.gmail.com>
Date:	Thu, 4 Sep 2008 12:17:14 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, "Krzysztof Helt" <krzysztof.h1@...pl>
Subject: Re: [PATCH 5/6] x86: move mtrr cpu cap setting early in early_init_xxxx

On Thu, Sep 4, 2008 at 12:13 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Yinghai Lu <yhlu.kernel@...il.com> wrote:
>
>> Krzysztof Helt <krzysztof.h1@...pl> found mtrr is not detected on k6-2
>>
>> root case:
>>       we move mtrr_bp_init early for mtrr trimming.
>> and in early_detect, only read cap from cpuid, so some cpu doesn't have
>> that bit in cpuid and need to set workaround bit will have problem.
>>
>> need to add early_init_xxxx to preset those bit before mtrr_bp_init
>> for those earlier cpus.
>>
>> this patch is for 2.6.27
>
> hm, not sure we can do it in v2.6.27 as it depends on the other CPU init
> patches and that is a rather sensitive codepath. This problem should be
> present in v2.6.26 too, right?

Yes. old cpus without cpuid bit for mtrr need this patch...
Krzysztof Helt tested it and it works with 2.6.27-rc5 (?)


YH
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