linux-kernel - [PATCH] Prevent AMD MCE oops on multi-server system

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Date:	Mon,  1 Oct 2012 14:42:05 +0800
From:	Daniel J Blueman <daniel@...ascale-asia.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Borislav Petkov <bp@...64.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Daniel J Blueman <daniel@...ascale-asia.com>
Subject: [PATCH] Prevent AMD MCE oops on multi-server system

When booting on a federated multi-server system, the processor Northbridge
lookup returns NULL; add guards to prevent this causing an oops.

Signed-off-by: Daniel J Blueman <daniel@...ascale-asia.com>
---
 arch/x86/kernel/cpu/mcheck/mce_amd.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index c4e916d..698b6ec 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -576,12 +576,10 @@ static __cpuinit int threshold_create_bank(unsigned int cpu, unsigned int bank)
 	int err = 0;
 
 	if (shared_bank[bank]) {
-
 		nb = node_to_amd_nb(amd_get_nb_id(cpu));
-		WARN_ON(!nb);
 
 		/* threshold descriptor already initialized on this node? */
-		if (nb->bank4) {
+		if (nb && nb->bank4) {
 			/* yes, use it */
 			b = nb->bank4;
 			err = kobject_add(b->kobj, &dev->kobj, name);
@@ -615,8 +613,10 @@ static __cpuinit int threshold_create_bank(unsigned int cpu, unsigned int bank)
 		atomic_set(&b->cpus, 1);
 
 		/* nb is already initialized, see above */
-		WARN_ON(nb->bank4);
-		nb->bank4 = b;
+		if (nb) {
+			WARN_ON(nb->bank4);
+			nb->bank4 = b;
+		}
 	}
 
 	err = allocate_threshold_blocks(cpu, bank, 0,
-- 
1.7.9.5

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