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Subject[PATCH] x86_64: make amd quad core 8 socket system not be clustered_box v2

quad core 8 socket system will have apic id lifting.the apic id range could
be [4, 0x23]. and 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 will check if the cpu is from AMD.

Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>

diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index d8d03e0..7d8ffda 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -1180,9 +1180,19 @@ __cpuinit int apic_is_clustered_box(void)
{
int i, clusters, zeros;
unsigned id;
- u16 *bios_cpu_apicid = x86_bios_cpu_apicid_early_ptr;
+ u16 *bios_cpu_apicid;
DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);

+ /*
+ * there is not this kind of box with AMD CPU yet.
+ * Some AMD box with quadcore cpu and 8 sockets apicid
+ * will be [4, 0x23] or [8, 0x27] could be thought to
+ * have three apic_clusters. So go out early.
+ */
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+ return 0;
+
+ bios_cpu_apicid = x86_bios_cpu_apicid_early_ptr;
bitmap_zero(clustermap, NUM_APIC_CLUSTERS);

for (i = 0; i < NR_CPUS; i++) {

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