2 files changed, 17 insertions, 3 deletions

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 4d3355da0e26..e71bc6cbbc5e 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -58,6 +58,12 @@ mark such hot-pluggable cpus as disabled entries, one could use this
 parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
 
 
+possible_cpus=n         [s390 only] use this to set hotpluggable cpus.
+                        This option sets possible_cpus bits in
+                        cpu_possible_map. Thus keeping the numbers of bits set
+                        constant even if the machine gets rebooted.
+                        This option overrides additional_cpus.
+
 CPU maps and such
 -----------------
 [More on cpumaps and primitive to manipulate, please check
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 53291e94ac7b..d0a2745aec7f 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -673,15 +673,16 @@ __cpu_up(unsigned int cpu)
 }
 
 static unsigned int __initdata additional_cpus;
+static unsigned int __initdata possible_cpus;
 
 void __init smp_setup_cpu_possible_map(void)
 {
         unsigned int pcpus, cpu;
 
-        pcpus = smp_count_cpus() + additional_cpus;
+        pcpus = min(smp_count_cpus() + additional_cpus, (unsigned int) NR_CPUS);
 
-        if (pcpus > NR_CPUS)
-                pcpus = NR_CPUS;
+        if (possible_cpus)
+                pcpus = min(possible_cpus, (unsigned int) NR_CPUS);
 
         for (cpu = 0; cpu < pcpus; cpu++)
                 cpu_set(cpu, cpu_possible_map);
@@ -698,6 +699,13 @@ static int __init setup_additional_cpus(char *s)
 }
 early_param("additional_cpus", setup_additional_cpus);
 
+static int __init setup_possible_cpus(char *s)
+{
+        possible_cpus = simple_strtoul(s, NULL, 0);
+        return 0;
+}
+early_param("possible_cpus", setup_possible_cpus);
+
 int
 __cpu_disable(void)
 {