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Subject[PATCH] x86_64: make amd quad core 8 socket system not be clustered_box

quad core 8 socket system will have apic id lifting.the apic id range could
be [4, 0x23]. or [8, 0x27]. apic_is_clustered_box will think that need to three clusters
and that is large than 2. So it is treated as clustered_box.

and will get

Marking TSC unstable due to TSCs unsynchronized

even the CPUs have X86_FEATURE_CONSTANT_TSC set.

this patch offset back the apic before get apic clusterid.

or use dmi to get apic_is_clustered?

Signed-off-by: Yinghai Lu <>

diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index 9b2be3d..5bdf1bc 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -1223,8 +1223,11 @@ __cpuinit int apic_is_clustered_box(void)

- if (id != BAD_APICID)
+ if (id != BAD_APICID) {
+ if (id >= boot_cpu_id)
+ id -= boot_cpu_id;
__set_bit(APIC_CLUSTERID(id), clustermap);
+ }

/* Problem: Partially populated chassis may not have CPUs in some of

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