2 files changed, 15 insertions, 11 deletions

diff --git a/arch/powerpc/include/asm/mpic.h b/arch/powerpc/include/asm/mpic.h
index df18989e78d4..e6fae49e0b74 100644
--- a/arch/powerpc/include/asm/mpic.h
+++ b/arch/powerpc/include/asm/mpic.h
@@ -273,8 +273,6 @@ struct mpic
         unsigned int            irq_count;
         /* Number of sources */
         unsigned int            num_sources;
-        /* Number of CPUs */
-        unsigned int            num_cpus;
         /* default senses array */
         unsigned char           *senses;
         unsigned int            senses_count;
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index d5d3ff3d757e..9678081dc4e2 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1285,13 +1285,11 @@ struct mpic * __init mpic_alloc(struct device_node *node,
                            mpic_read(mpic->gregs, MPIC_INFO(GREG_GLOBAL_CONF_0))
                            | MPIC_GREG_GCONF_MCK);
 
-        /* Read feature register, calculate num CPUs and, for non-ISU
-         * MPICs, num sources as well. On ISU MPICs, sources are counted
-         * as ISUs are added
+        /*
+         * Read feature register.  For non-ISU MPICs, num sources as well. On
+         * ISU MPICs, sources are counted as ISUs are added
          */
         greg_feature = mpic_read(mpic->gregs, MPIC_INFO(GREG_FEATURE_0));
-        mpic->num_cpus = ((greg_feature & MPIC_GREG_FEATURE_LAST_CPU_MASK)
-                          >> MPIC_GREG_FEATURE_LAST_CPU_SHIFT) + 1;
         if (isu_size == 0) {
                 if (flags & MPIC_BROKEN_FRR_NIRQS)
                         mpic->num_sources = mpic->irq_count;
@@ -1301,10 +1299,18 @@ struct mpic * __init mpic_alloc(struct device_node *node,
                                  >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT) + 1;
         }
 
+        /*
+         * The MPIC driver will crash if there are more cores than we
+         * can initialize, so we may as well catch that problem here.
+         */
+        BUG_ON(num_possible_cpus() > MPIC_MAX_CPUS);
+
         /* Map the per-CPU registers */
-        for (i = 0; i < mpic->num_cpus; i++) {
-                mpic_map(mpic, node, paddr, &mpic->cpuregs[i],
-                         MPIC_INFO(CPU_BASE) + i * MPIC_INFO(CPU_STRIDE),
+        for_each_possible_cpu(i) {
+                unsigned int cpu = get_hard_smp_processor_id(i);
+
+                mpic_map(mpic, node, paddr, &mpic->cpuregs[cpu],
+                         MPIC_INFO(CPU_BASE) + cpu * MPIC_INFO(CPU_STRIDE),
                          0x1000);
         }
 
@@ -1343,7 +1349,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
         }
         printk(KERN_INFO "mpic: Setting up MPIC \"%s\" version %s at %llx,"
                " max %d CPUs\n",
-               name, vers, (unsigned long long)paddr, mpic->num_cpus);
+               name, vers, (unsigned long long)paddr, num_possible_cpus());
         printk(KERN_INFO "mpic: ISU size: %d, shift: %d, mask: %x\n",
                mpic->isu_size, mpic->isu_shift, mpic->isu_mask);