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

Ingo Molnar
2008-08-22T06:25:58Z

* Yinghai Lu <yhlu.kernel@gmail.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@elte.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@elte.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;
}
}