diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 20a6142..3dd53f9 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1721,10 +1721,8 @@
 		machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
 	}
 #ifdef CONFIG_X86_32
-	if ((machine_to_phys_mapping + machine_to_phys_nr)
-	    < machine_to_phys_mapping)
-		machine_to_phys_nr = (unsigned long *)NULL
-				     - machine_to_phys_mapping;
+	WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
+		< machine_to_phys_mapping);
 #endif
 }
 
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c3b8d44..46d6d21 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -306,10 +306,12 @@
 	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 
 	extra_limit = xen_get_max_pages();
-	if (extra_limit >= max_pfn)
-		extra_pages = extra_limit - max_pfn;
-	else
-		extra_pages = 0;
+	if (max_pfn + extra_pages > extra_limit) {
+		if (extra_limit > max_pfn)
+			extra_pages = extra_limit - max_pfn;
+		else
+			extra_pages = 0;
+	}
 
 	extra_pages += xen_return_unused_memory(xen_start_info->nr_pages, &e820);
 
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index d4fc6d4..041d4fe 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -532,7 +532,6 @@
 	WARN_ON(xen_smp_intr_init(0));
 
 	xen_init_lock_cpu(0);
-	xen_init_spinlocks();
 }
 
 static int __cpuinit xen_hvm_cpu_up(unsigned int cpu)
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index da70f5c..7523719 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -54,7 +54,7 @@
  * This lock protects updates to the following mapping and reference-count
  * arrays. The lock does not need to be acquired to read the mapping tables.
  */
-static DEFINE_SPINLOCK(irq_mapping_update_lock);
+static DEFINE_MUTEX(irq_mapping_update_lock);
 
 static LIST_HEAD(xen_irq_list_head);
 
@@ -631,7 +631,7 @@
 	int irq = -1;
 	struct physdev_irq irq_op;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = find_irq_by_gsi(gsi);
 	if (irq != -1) {
@@ -684,7 +684,7 @@
 				handle_edge_irq, name);
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -710,7 +710,7 @@
 {
 	int irq, ret;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = xen_allocate_irq_dynamic();
 	if (irq == -1)
@@ -724,10 +724,10 @@
 	if (ret < 0)
 		goto error_irq;
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return irq;
 error_irq:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	xen_free_irq(irq);
 	return -1;
 }
@@ -740,7 +740,7 @@
 	struct irq_info *info = info_for_irq(irq);
 	int rc = -ENOENT;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	desc = irq_to_desc(irq);
 	if (!desc)
@@ -766,7 +766,7 @@
 	xen_free_irq(irq);
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return rc;
 }
 
@@ -776,7 +776,7 @@
 
 	struct irq_info *info;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	list_for_each_entry(info, &xen_irq_list_head, list) {
 		if (info == NULL || info->type != IRQT_PIRQ)
@@ -787,7 +787,7 @@
 	}
 	irq = -1;
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -802,7 +802,7 @@
 {
 	int irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = evtchn_to_irq[evtchn];
 
@@ -818,7 +818,7 @@
 	}
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -829,7 +829,7 @@
 	struct evtchn_bind_ipi bind_ipi;
 	int evtchn, irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = per_cpu(ipi_to_irq, cpu)[ipi];
 
@@ -853,7 +853,7 @@
 	}
 
  out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return irq;
 }
 
@@ -878,7 +878,7 @@
 	struct evtchn_bind_virq bind_virq;
 	int evtchn, irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = per_cpu(virq_to_irq, cpu)[virq];
 
@@ -903,7 +903,7 @@
 	}
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -913,7 +913,7 @@
 	struct evtchn_close close;
 	int evtchn = evtchn_from_irq(irq);
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	if (VALID_EVTCHN(evtchn)) {
 		close.port = evtchn;
@@ -943,7 +943,7 @@
 
 	xen_free_irq(irq);
 
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 }
 
 int bind_evtchn_to_irqhandler(unsigned int evtchn,
@@ -1279,7 +1279,7 @@
 	   will also be masked. */
 	disable_irq(irq);
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	/* After resume the irq<->evtchn mappings are all cleared out */
 	BUG_ON(evtchn_to_irq[evtchn] != -1);
@@ -1289,7 +1289,7 @@
 
 	xen_irq_info_evtchn_init(irq, evtchn);
 
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	/* new event channels are always bound to cpu 0 */
 	irq_set_affinity(irq, cpumask_of(0));