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, 2 insertions, 1 deletions

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 943d814ef8e4..2fc696e4d565 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -4109,7 +4109,8 @@ void __init pre_init_apic_IRQ0(void)
 
         printk(KERN_INFO "Early APIC setup for system timer0\n");
 #ifndef CONFIG_SMP
-        phys_cpu_present_map = physid_mask_of_physid(boot_cpu_physical_apicid);
+        physid_set_mask_of_physid(boot_cpu_physical_apicid,
+                                         &phys_cpu_present_map);
 #endif
         /* Make sure the irq descriptor is set up */
         cfg = alloc_irq_and_cfg_at(0, 0);