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Subject[PATCH] [85/139] x86, amd: Fix panic on AMD CPU family 0x15
Date
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Andreas Herrmann <andreas.herrmann3@amd.com>

[The mainline kernel doesn't have this problem. Commit "(23588c3) x86,
amd: Add support for CPUID topology extension of AMD CPUs" removed the
family check. But 2.6.32.y needs to be fixed.]

This CPU family check is not required -- existence of the NodeId MSR
is indicated by a CPUID feature flag which is already checked in
amd_fixup_dcm() -- and it needlessly prevents amd_fixup_dcm() to be
called for newer AMD CPUs.

In worst case this can lead to a panic in the scheduler code for AMD
family 0x15 multi-node AMD CPUs. I just have a picture of VGA console
output so I can't copy-and-paste it herein, but the call stack of such
a panic looked like:

do_divide_error
...
find_busiest_group
run_rebalance_domains
...
apic_timer_interrupt
...
cpu_idle

The mainline kernel doesn't have this problem. Commit "(23588c3) x86,
amd: Add support for CPUID topology extension of AMD CPUs" removed the
family check. But 2.6.32.y needs to be fixed.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
arch/x86/kernel/cpu/amd.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-2.6.35.y/arch/x86/kernel/cpu/amd.c
===================================================================
--- linux-2.6.35.y.orig/arch/x86/kernel/cpu/amd.c
+++ linux-2.6.35.y/arch/x86/kernel/cpu/amd.c
@@ -305,8 +305,7 @@ static void __cpuinit amd_detect_cmp(str
/* use socket ID also for last level cache */
per_cpu(cpu_llc_id, cpu) = c->phys_proc_id;
/* fixup topology information on multi-node processors */
- if ((c->x86 == 0x10) && (c->x86_model == 9))
- amd_fixup_dcm(c);
+ amd_fixup_dcm(c);
#endif
}


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