Re: [PATCH] x86: fdiv bug detection fix
- From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 31 Jul 2008 14:49:20 -0700
On Thu, 31 Jul 2008 23:43:44 +0200
Krzysztof Helt <krzysztof.h1@xxxxx> wrote:
From: Krzysztof Helt <krzysztof.h1@xxxxx>
The fdiv detection code writes s32 integer into
the boot_cpu_data.fdiv_bug.
However, the boot_cpu_data.fdiv_bug is only char (s8)
field so the detection overwrites already set fields for
other bugs, e.g. the f00f bug field.
Use local s32 variable to receive result.
Signed-off-by: Krzysztof Helt <krzysztof.h1@xxxxx>
---
This is a partial fix to Bugzilla #9928 - fixes wrong
information about the f00f bug (tested) and probably
for coma bug (I have no cpu to test this).
diff -urp linux-alsa/arch/x86/kernel/cpu/bugs.c linux-new/arch/x86/kernel/cpu/bugs.c
--- linux-alsa/arch/x86/kernel/cpu/bugs.c 2008-07-31 12:40:31.000000000 +0200
+++ linux-new/arch/x86/kernel/cpu/bugs.c 2008-07-31 23:24:07.722657435 +0200
@@ -50,6 +50,8 @@ static double __initdata y = 3145727.0;
*/
static void __init check_fpu(void)
{
+ s32 fdiv_bug;
+
if (!boot_cpu_data.hard_math) {
#ifndef CONFIG_MATH_EMULATION
printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
@@ -74,8 +76,10 @@ static void __init check_fpu(void)
"fistpl %0\n\t"
"fwait\n\t"
"fninit"
- : "=m" (*&boot_cpu_data.fdiv_bug)
+ : "=m" (*&fdiv_bug)
: "m" (*&x), "m" (*&y));
+
+ boot_cpu_data.fdiv_bug = fdiv_bug;
if (boot_cpu_data.fdiv_bug)
printk("Hmm, FPU with FDIV bug.\n");
}
hm, the code seems to have been that way for quite some time. I wonder
why nobody noticed this before.
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- From: Krzysztof Helt
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