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* [PATCH] x86, 64bit: Always make MAX_APICS to 32768
@ 2010-12-31  1:05 Yinghai Lu
  2011-01-04  8:48 ` Ingo Molnar
  0 siblings, 1 reply; 5+ messages in thread
From: Yinghai Lu @ 2010-12-31  1:05 UTC (permalink / raw)
  To: H. Peter Anvin, Ingo Molnar, Thomas Gleixner; +Cc: linux-kernel@vger.kernel.org


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) cause the problem.

phys_cpu_present_map is with MAX_APICS bits. and pre-enabled system some cpus apic id > 255.

the variable after phys_cpu_present_map may get corrupted.... siliently...

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_APICIS. but that is another header.

So just let MAX_APICS equal to MAX_LOCAL_APIC at this point.
esp for 64 bit will be 32768 in all cases.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/include/asm/mpspec_def.h |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

Index: linux-2.6/arch/x86/include/asm/mpspec_def.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/mpspec_def.h
+++ linux-2.6/arch/x86/include/asm/mpspec_def.h
@@ -17,11 +17,7 @@
 # define MAX_MPC_ENTRY 1024
 # define MAX_APICS      256
 #else
-# if NR_CPUS <= 255
-#  define MAX_APICS     255
-# else
-#  define MAX_APICS   32768
-# endif
+# define MAX_APICS    32768
 #endif
 
 /* Intel MP Floating Pointer Structure */

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2011-01-05 14:07 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2010-12-31  1:05 [PATCH] x86, 64bit: Always make MAX_APICS to 32768 Yinghai Lu
2011-01-04  8:48 ` Ingo Molnar
2011-01-05  0:38   ` Yinghai Lu
2011-01-05 13:10     ` Ingo Molnar
2011-01-05 14:06     ` [tip:x86/apic] x86: Fix APIC ID sizing bug on larger systems, clean up MAX_APICS confusion tip-bot for Yinghai Lu

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