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

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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>
This commit is contained in:
Yinghai Lu
2011-01-04 16:38:52 -08:00
committed by Ingo Molnar
parent bc030d6cb9
commit cb2ded37fd
6 changed files with 19 additions and 32 deletions
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7
arch/x86/include/asm/mpspec_def.h
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@@ -15,13 +15,6 @@
#ifdef CONFIG_X86_32
# define MAX_MPC_ENTRY 1024
# define MAX_APICS 256
#else
# if NR_CPUS <= 255
# define MAX_APICS 255
# else
# define MAX_APICS 32768
# endif
#endif
/* Intel MP Floating Pointer Structure */