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

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Date:	Mon, 1 Sep 2008 18:16:42 +0200
From:	Krzysztof Helt <krzysztof.h1@...zta.fm>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Krzysztof Helt <krzysztof.h1@...pl>
Subject: Re: [PATCH] x86: move mtrr cpu cap setting early in early_init_xxxx

On Sun, 31 Aug 2008 21:07:05 -0700
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
> 
> Reported-by: Krzysztof Helt <krzysztof.h1@...pl>
> Signed-off-by: Yinghai Lu <yhlu.kernel@...il.com>
> Cc: Krzysztof Helt <krzysztof.h1@...pl>
> 
> ---

Your patch works only if the the fix below is applied.

Otherwise, the caps set in the early_cpu_init are reset
in the early_get_cap.

Regards,
Krzysztof

---
>From 808cfe180c1400594a01d6229239d4bf01ca4eea Mon Sep 17 00:00:00 2001
From: Krzysztof Helt <krzysztof.h1@...pl>
Date: Tue, 2 Sep 2008 17:29:51 +0200
Subject: [PATCH] x86: delay early cpu initialization until cpuid is done

Move early cpu initialization after cpu
early get cap so the early cpu initialization
can fix up cpu caps.

Signed-off-by: Krzysztof Helt <krzysztof.h1@...pl>
---
 arch/x86/kernel/cpu/common.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d3bc82f..f970cbf 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -335,11 +335,11 @@ static void __init early_cpu_detect(void)
 
 	get_cpu_vendor(c, 1);
 
+	early_get_cap(c);
+
 	if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
 	    cpu_devs[c->x86_vendor]->c_early_init)
 		cpu_devs[c->x86_vendor]->c_early_init(c);
-
-	early_get_cap(c);
 }
 
 /*
-- 
1.5.2.2




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