s390/smp: improve setup of possible cpu mask

Since under z/VM we cannot have more than 64 cpus, make sure the
cpu_possible_mask does not contain more bits.
This avoids wasting memory for dynamic per-cpu allocations if
CONFIG_NR_CPUS is larger than 64.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 16 insertions, 9 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index dc4a53465060..958704798f4a 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -721,18 +721,14 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
         return 0;
 }
 
-static int __init setup_possible_cpus(char *s)
-{
-        int max, cpu;
+static unsigned int setup_possible_cpus __initdata;
 
-        if (kstrtoint(s, 0, &max) < 0)
-                return 0;
-        init_cpu_possible(cpumask_of(0));
-        for (cpu = 1; cpu < max && cpu < nr_cpu_ids; cpu++)
-                set_cpu_possible(cpu, true);
+static int __init _setup_possible_cpus(char *s)
+{
+        get_option(&s, &setup_possible_cpus);
         return 0;
 }
-early_param("possible_cpus", setup_possible_cpus);
+early_param("possible_cpus", _setup_possible_cpus);
 
 #ifdef CONFIG_HOTPLUG_CPU
 
@@ -775,6 +771,17 @@ void __noreturn cpu_die(void)
 
 #endif /* CONFIG_HOTPLUG_CPU */
 
+void __init smp_fill_possible_mask(void)
+{
+        unsigned int possible, cpu;
+
+        possible = setup_possible_cpus;
+        if (!possible)
+                possible = MACHINE_IS_VM ? 64 : nr_cpu_ids;
+        for (cpu = 0; cpu < possible && cpu < nr_cpu_ids; cpu++)
+                set_cpu_possible(cpu, true);
+}
+
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
         /* request the 0x1201 emergency signal external interrupt */