x86: fix 2.6.27rc1 cannot boot more than 8CPUs

Jeff Chua reported that booting a !bigsmp kernel on a 16-way box
hangs silently.

this is a long-standing issue, smp start AP cpu could check the
apic id >=8 etc before trying to start it.

achieve this by moving the def_to_bigsmp check later and skip the
apicid id > 8

[ mingo@elte.hu: clean up the message that is printed. ]

Reported-by: "Jeff Chua" <jeff.chua.linux@gmail.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

 arch/x86/kernel/setup.c   |    6 ------
 arch/x86/kernel/smpboot.c |   10 ++++++++++
 2 files changed, 10 insertions(+), 6 deletions(-)

2 files changed, 10 insertions, 6 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 6e5823b9e765..68b48e3fbcbd 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -861,12 +861,6 @@ void __init setup_arch(char **cmdline_p)
         init_apic_mappings();
         ioapic_init_mappings();
 
-#if defined(CONFIG_SMP) && defined(CONFIG_X86_PC) && defined(CONFIG_X86_32)
-        if (def_to_bigsmp)
-                printk(KERN_WARNING "More than 8 CPUs detected and "
-                        "CONFIG_X86_PC cannot handle it.\nUse "
-                        "CONFIG_X86_GENERICARCH or CONFIG_X86_BIGSMP.\n");
-#endif
         kvm_guest_init();
 
         e820_reserve_resources();
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index da10f07fc59c..91055d7fc1b0 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -994,7 +994,17 @@ int __cpuinit native_cpu_up(unsigned int cpu)
         flush_tlb_all();
         low_mappings = 1;
 
+#ifdef CONFIG_X86_PC
+        if (def_to_bigsmp && apicid > 8) {
+                printk(KERN_WARNING
+                        "More than 8 CPUs detected - skipping them.\n"
+                        "Use CONFIG_X86_GENERICARCH and CONFIG_X86_BIGSMP.\n");
+                err = -1;
+        } else
+                err = do_boot_cpu(apicid, cpu);
+#else
         err = do_boot_cpu(apicid, cpu);
+#endif
 
         zap_low_mappings();
         low_mappings = 0;