x86_64: set cpu_index to NR_CPUS instead of 0

[PATCH] x86_64: set cpu_index to NR_CPUS instead of 0

same BIOS will support two/four dualcore/quadcore system, and will get

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled) Processor #0 15:1 APIC version 16
ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled) Processor #1 15:1 APIC version 16
ACPI: LAPIC (acpi_id[0x03] lapic_id[0x02] enabled) Processor #2 15:1 APIC version 16
ACPI: LAPIC (acpi_id[0x04] lapic_id[0x03] enabled) Processor #3 15:1 APIC version 16
ACPI: LAPIC (acpi_id[0x05] lapic_id[0x84] disabled)
ACPI: LAPIC (acpi_id[0x06] lapic_id[0x85] disabled)
ACPI: LAPIC (acpi_id[0x07] lapic_id[0x86] disabled)
ACPI: LAPIC (acpi_id[0x08] lapic_id[0x87] disabled)
ACPI: LAPIC (acpi_id[0x09] lapic_id[0x88] disabled)
ACPI: LAPIC (acpi_id[0x0a] lapic_id[0x89] disabled)
ACPI: LAPIC (acpi_id[0x0b] lapic_id[0x8a] disabled)
ACPI: LAPIC (acpi_id[0x0c] lapic_id[0x8b] disabled)
ACPI: LAPIC (acpi_id[0x0d] lapic_id[0x8c] disabled)
ACPI: LAPIC (acpi_id[0x0e] lapic_id[0x8d] disabled)
ACPI: LAPIC (acpi_id[0x0f] lapic_id[0x8e] disabled)
ACPI: LAPIC (acpi_id[0x10] lapic_id[0x8f] disabled)

SMP: Allowing 16 CPUs, 12 hotplug CPUs

the /proc/cpuinfo will show as bunch of NULL cpus with cpu_index=0

so assign impossible cpu_index value at first instead of 0.

Index: linux-2.6/arch/x86/kernel/smpboot_64.c
===================================================================
@@ -861,6 +861,18 @@ void __init smp_set_apicids(void)
 	x86_cpu_to_apicid_ptr = NULL;
 }
 
+static void __init smp_cpu_index_default(void)
+{
+	int i;
+	struct cpuinfo_x86 *c;
+
+	for_each_cpu_mask(i, cpu_possible_map) {
+		c = &cpu_data(i);
+		/* mark all to hotplug */
+		c->cpu_index = NR_CPUS;
+	}
+}
+
 /*
  * Prepare for SMP bootup.  The MP table or ACPI has been read
  * earlier.  Just do some sanity checking here and enable APIC mode.

@@ -868,6 +880,7 @@ void __init smp_set_apicids(void)
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 	nmi_watchdog_default();
+	smp_cpu_index_default();
 	current_cpu_data = boot_cpu_data;
 	current_thread_info()->cpu = 0;  /* needed? */
 	smp_set_apicids();