This is a note to let you know that I've just added the patch titled
x86/mce: Fix check for processor context when machine check was taken.
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mce-fix-check-for-processor-context-when-machine-check-was-taken.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 875e26648cf9b6db9d8dc07b7959d7c61fb3f49c Mon Sep 17 00:00:00 2001
From: Tony Luck <[email protected]>
Date: Wed, 23 May 2012 14:14:22 -0700
Subject: x86/mce: Fix check for processor context when machine check was taken.
From: Tony Luck <[email protected]>
commit 875e26648cf9b6db9d8dc07b7959d7c61fb3f49c upstream.
Linus pointed out that there was no value is checking whether m->ip
was zero - because zero is a legimate value. If we have a reliable
(or faked in the VM86 case) "m->cs" we can use it to tell whether we
were in user mode or kernelwhen the machine check hit.
Reported-by: Linus Torvalds <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/cpu/mcheck/mce-severity.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -101,15 +101,19 @@ static struct severity {
};
/*
- * If the EIPV bit is set, it means the saved IP is the
- * instruction which caused the MCE.
+ * If mcgstatus indicated that ip/cs on the stack were
+ * no good, then "m->cs" will be zero and we will have
+ * to assume the worst case (IN_KERNEL) as we actually
+ * have no idea what we were executing when the machine
+ * check hit.
+ * If we do have a good "m->cs" (or a faked one in the
+ * case we were executing in VM86 mode) we can use it to
+ * distinguish an exception taken in user from from one
+ * taken in the kernel.
*/
static int error_context(struct mce *m)
{
- if (m->mcgstatus & MCG_STATUS_EIPV)
- return (m->ip && (m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
- /* Unknown, assume kernel */
- return IN_KERNEL;
+ return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
}
int mce_severity(struct mce *a, int tolerant, char **msg)
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/x86-mce-fix-check-for-processor-context-when-machine-check-was-taken.patch
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