linux-kernel - Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of 16gb of memory is usable

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Date:	Fri, 22 Aug 2008 08:24:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Joshua Hoblitt <josh@...litt.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org,
	j_kernel@...litt.com, Arjan van de Ven <arjan@...radead.org>
Subject: Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of
	16gb of memory is usable


* Yinghai Lu <yhlu.kernel@...il.com> wrote:

> > +               if (tmp != mask_lo) {
> > +                       WARN_ON("mtrr: your BIOS has set up an incorrect mask, fixing it up.\n");
> 
> can you change WARN_ON to WARN_ON_ONCE ?

the commit below does that. Note that the condition is 
WARN_ON(condition) or WARN(string) - WARN_ON(string) will just print a 
kernel stack unconditionally. Unfortunately there's no WARN_ONCE(). 
(Arjan?)

	Ingo

---------->
>From 1c8aa33e17dc4aa68b329d262fff253648a98adb Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@...e.hu>
Date: Fri, 22 Aug 2008 08:22:23 +0200
Subject: [PATCH] x86: work around MTRR mask setting, v2

improve the debug printout:

- make it actually display something
- print it only once

would be nice to have a WARN_ONCE() facility, to feed such things to
kerneloops.org.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/kernel/cpu/mtrr/generic.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 43102e0..cb7d3b6 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -401,7 +401,12 @@ static void generic_get_mtrr(unsigned int reg, unsigned long *base,
 		tmp |= ~((1<<(hi - 1)) - 1);
 
 		if (tmp != mask_lo) {
-			WARN_ON("mtrr: your BIOS has set up an incorrect mask, fixing it up.\n");
+			static int once = 1;
+
+			if (once) {
+				printk(KERN_INFO "mtrr: your BIOS has set up an incorrect mask, fixing it up.\n");
+				once = 0;
+			}
 			mask_lo = tmp;
 		}
 	}
--
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