+ int i, clusters, zeros;
+ unsigned id;
+ 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
+ * vsmp box still need checking...
+ */
+ if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
+ return 0;
+
+ bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);
+ bitmap_zero(clustermap, NUM_APIC_CLUSTERS);
+
+ for (i = 0; i < NR_CPUS; i++) {
+ /* are we being called early in kernel startup? */
+ if (bios_cpu_apicid) {
+ id = bios_cpu_apicid[i];
+ }
+ else if (i < nr_cpu_ids) {
+ if (cpu_present(i))
+ id = per_cpu(x86_bios_cpu_apicid, i);
+ else
+ continue;
+ }
+ else
+ break;
+
+ if (id != BAD_APICID)
+ __set_bit(APIC_CLUSTERID(id), clustermap);
+ }
+
+ /* Problem: Partially populated chassis may not have CPUs in some of
+ * the APIC clusters they have been allocated. Only present CPUs have
+ * x86_bios_cpu_apicid entries, thus causing zeroes in the bitmap.
+ * Since clusters are allocated sequentially, count zeros only if
+ * they are bounded by ones.
+ */
+ clusters = 0;
+ zeros = 0;
+ for (i = 0; i < NUM_APIC_CLUSTERS; i++) {
+ if (test_bit(i, clustermap)) {
+ clusters += 1 + zeros;
+ zeros = 0;
+ } else
+ ++zeros;
+ }
+
+ /* ScaleMP vSMPowered boxes have one cluster per board and TSCs are
+ * not guaranteed to be synced between boards
+ */
+ if (is_vsmp_box() && clusters > 1)
+ return 1;
+
+ /*
+ * If clusters > 2, then should be multi-chassis.
+ * May have to revisit this when multi-core + hyperthreaded CPUs come
+ * out, but AFAIK this will work even for them.
+ */
+ return (clusters > 2);