ACPI: boot correctly with "nosmp" or "maxcpus=0"

In MPS mode, "nosmp" and "maxcpus=0" boot a UP kernel with IOAPIC disabled.
However, in ACPI mode, these parameters didn't completely disable
the IO APIC initialization code and boot failed.

init/main.c:
	Disable the IO_APIC if "nosmp" or "maxcpus=0"
	undefine disable_ioapic_setup() when it doesn't apply.

i386:
	delete ioapic_setup(), it was a duplicate of parse_noapic()
	delete undefinition of disable_ioapic_setup()

x86_64:
	rename disable_ioapic_setup() to parse_noapic() to match i386
	define disable_ioapic_setup() in header to match i386

http://bugzilla.kernel.org/show_bug.cgi?id=1641

Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 6 insertions, 9 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 975f029be25c..17770b456310 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -952,14 +952,10 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format: <1-256>
 
         maxcpus=        [SMP] Maximum number of processors that an SMP kernel
-                        should make use of.
-                        Using "nosmp" or "maxcpus=0" will disable SMP
-                        entirely (the MPS table probe still happens, though).
-                        A command-line option of "maxcpus=<NUM>", where <NUM>
-                        is an integer greater than 0, limits the maximum number
-                        of CPUs activated in SMP mode to <NUM>.
-                        Using "maxcpus=1" on an SMP kernel is the trivial
-                        case of an SMP kernel with only one CPU.
+                        should make use of.  maxcpus=n : n >= 0 limits the
+                        kernel to using 'n' processors.  n=0 is a special case,
+                        it is equivalent to "nosmp", which also disables
+                        the IO APIC.
 
         max_addr=[KMG]  [KNL,BOOT,ia64] All physical memory greater than or
                         equal to this physical address is ignored.
@@ -1184,7 +1180,8 @@ and is between 256 and 4096 characters. It is defined in the file
 
         nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
 
-        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.
+        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
+                        and disable the IO APIC.  legacy for "maxcpus=0".
 
         nosoftlockup    [KNL] Disable the soft-lockup detector.