x86: Fix APIC ID sizing bug on larger systems, clean up MAX_APICS confusion

Found one x2apic pre-enabled system, x2apic_mode suddenly get
corrupted after register some cpus, when compiled
CONFIG_NR_CPUS=255 instead of 512.

It turns out that generic_processor_info() ==> phyid_set(apicid,
phys_cpu_present_map) causes the problem.

phys_cpu_present_map is sized by MAX_APICS bits, and pre-enabled
system some cpus have an apic id > 255.

The variable after phys_cpu_present_map may get corrupted
silently:

 ffffffff828e8420 B phys_cpu_present_map
 ffffffff828e8440 B apic_verbosity
 ffffffff828e8444 B local_apic_timer_c2_ok
 ffffffff828e8448 B disable_apic
 ffffffff828e844c B x2apic_mode
 ffffffff828e8450 B x2apic_disabled
 ffffffff828e8454 B num_processors
 ...

Actually phys_cpu_present_map is referenced via apic id, instead
index. We should use MAX_LOCAL_APIC instead MAX_APICS.

For 64-bit it will be 32768 in all cases. BSS will increase by 4k bytes
on 64-bit:

	text		data		bss		dec		filename
	21696943	4193748		12787712	38678403	vmlinux.before
	21696943	4193748		12791808	38682499	vmlinux.after

No change on 32bit.

Finally we can remove MAX_APCIS that was rather confusing.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
LKML-Reference: <4D23BD9C.3070102@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 7235e5fbdb6d..17c8090fabd4 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -915,13 +915,13 @@ static int __init acpi_parse_madt_lapic_entries(void)
         acpi_register_lapic_address(acpi_lapic_addr);
 
         count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
-                                      acpi_parse_sapic, MAX_APICS);
+                                      acpi_parse_sapic, MAX_LOCAL_APIC);
 
         if (!count) {
                 x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC,
-                                                acpi_parse_x2apic, MAX_APICS);
+                                        acpi_parse_x2apic, MAX_LOCAL_APIC);
                 count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
-                                              acpi_parse_lapic, MAX_APICS);
+                                        acpi_parse_lapic, MAX_LOCAL_APIC);
         }
         if (!count && !x2count) {
                 printk(KERN_ERR PREFIX "No LAPIC entries present\n");