Dont record local apic ids when they are disabled in MADT

[Ashok Raj <ashok.raj@intel.com>]

Hi Andrew,

We had added additional_cpus=xx for x86_64, but apparently there were some
BIOSs that had duplicate apic ids when they were reported disabled.

It seems fair not to record them, this was causing some bad behaviour due to
the duplicate apic id. More details in the bugzilla recorded in the log.

Please help with inclusion.


-- 
Cheers,
Ashok Raj
- Open Source Technology Center


Some broken BIOS's had processors disabled, but 
same apic id as a valid processor. This causes
acpi_processor_start() to think this disabled 
cpu is ok, and croak. So we dont record bad
apicid's anymore.

http://bugzilla.kernel.org/show_bug.cgi?id=5930

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
------------------------------------------------------
 arch/i386/kernel/acpi/boot.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

Index: linux-2.6.16-rc1-mm2/arch/i386/kernel/acpi/boot.c
===================================================================
--- linux-2.6.16-rc1-mm2.orig/arch/i386/kernel/acpi/boot.c
+++ linux-2.6.16-rc1-mm2/arch/i386/kernel/acpi/boot.c
@@ -248,10 +248,17 @@ acpi_parse_lapic(acpi_table_entry_header
 
 	acpi_table_print_madt_entry(header);
 
-	/* Register even disabled CPUs for cpu hotplug */
-
-	x86_acpiid_to_apicid[processor->acpi_id] = processor->id;
+	/* Record local apic id only when enabled */
+	if (processor->flags.enabled)
+		x86_acpiid_to_apicid[processor->acpi_id] = processor->id;
 
+	/*
+	 * We need to register disabled CPU as well to permit
+	 * counting disabled CPUs. This allows us to size
+	 * cpus_possible_map more accurately, to permit
+	 * to not preallocating memory for all NR_CPUS
+	 * when we use CPU hotplug.
+	 */
 	mp_register_lapic(processor->id,	/* APIC ID */
 			  processor->flags.enabled);	/* Enabled? */