doc: make doc. for maxcpus= more visible

Some people are confused about maxcpus=1 and maxcpus=0,
so put the documentation text from init/main.c into
Documentation/kernel-parameters.txt also.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

1 files changed, 8 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index abd575cfc759..f6a3961da349 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -863,7 +863,14 @@ 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
+                        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.
 
         max_addr=[KMG]  [KNL,BOOT,ia64] All physical memory greater than or
                         equal to this physical address is ignored.