1 files changed, 81 insertions, 0 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index 7cbd0f293df4..73a195193558 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -604,6 +604,87 @@ void ipi_call_unlock_irq(void)
 }
 #endif /* USE_GENERIC_SMP_HELPERS */
 
+/* Setup configured maximum number of CPUs to activate */
+unsigned int setup_max_cpus = NR_CPUS;
+EXPORT_SYMBOL(setup_max_cpus);
+
+
+/*
+ * Setup routine for controlling SMP activation
+ *
+ * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
+ * activation entirely (the MPS table probe still happens, though).
+ *
+ * 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>.
+ */
+
+void __weak arch_disable_smp_support(void) { }
+
+static int __init nosmp(char *str)
+{
+        setup_max_cpus = 0;
+        arch_disable_smp_support();
+
+        return 0;
+}
+
+early_param("nosmp", nosmp);
+
+/* this is hard limit */
+static int __init nrcpus(char *str)
+{
+        int nr_cpus;
+
+        get_option(&str, &nr_cpus);
+        if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
+                nr_cpu_ids = nr_cpus;
+
+        return 0;
+}
+
+early_param("nr_cpus", nrcpus);
+
+static int __init maxcpus(char *str)
+{
+        get_option(&str, &setup_max_cpus);
+        if (setup_max_cpus == 0)
+                arch_disable_smp_support();
+
+        return 0;
+}
+
+early_param("maxcpus", maxcpus);
+
+/* Setup number of possible processor ids */
+int nr_cpu_ids __read_mostly = NR_CPUS;
+EXPORT_SYMBOL(nr_cpu_ids);
+
+/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
+void __init setup_nr_cpu_ids(void)
+{
+        nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
+}
+
+/* Called by boot processor to activate the rest. */
+void __init smp_init(void)
+{
+        unsigned int cpu;
+
+        /* FIXME: This should be done in userspace --RR */
+        for_each_present_cpu(cpu) {
+                if (num_online_cpus() >= setup_max_cpus)
+                        break;
+                if (!cpu_online(cpu))
+                        cpu_up(cpu);
+        }
+
+        /* Any cleanup work */
+        printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
+        smp_cpus_done(setup_max_cpus);
+}
+
 /*
  * Call a function on all processors.  May be used during early boot while
  * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead