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x86, amd, mce: Avoid NULL pointer reference on CPU northbridge lookup
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When booting on a federated multi-server system (NumaScale), the
processor Northbridge lookup returns NULL; add guards to prevent this
causing an oops.

On those systems, the northbridge is accessed through MMIO and the
"normal" northbridge enumeration in amd_nb.c doesn't work since we're
generating the northbridge ID from the initial APIC ID and the last
is not unique on those systems. Long story short, we end up without
northbridge descriptors.

Signed-off-by: Daniel J Blueman <daniel@numascale-asia.com>
Cc: stable@vger.kernel.org # 3.6
Link: http://lkml.kernel.org/r/1349073725-14093-1-git-send-email-daniel@numascale-asia.com
[ Boris: beef up commit message ]
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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Daniel J Blueman authored and H. Peter Anvin committed Oct 17, 2012
1 parent 1bbbbe7 commit 21c5e50
Showing 1 changed file with 5 additions and 5 deletions.
10 changes: 5 additions & 5 deletions arch/x86/kernel/cpu/mcheck/mce_amd.c
Original file line number Diff line number Diff line change
@@ -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,

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