[PATCH] x86_64: Dont record local apic ids when they are disabled in MADT

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>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index f21fa0d4482f..79577f0ace98 100644
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -248,10 +248,17 @@ acpi_parse_lapic(acpi_table_entry_header * header, const unsigned long end)
 
         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? */