diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
index 8bff7e7c290b..1b2b73ff0a6e 100644
--- a/arch/x86/xen/multicalls.c
+++ b/arch/x86/xen/multicalls.c
@@ -189,10 +189,10 @@ struct multicall_space __xen_mc_entry(size_t args)
 	unsigned argidx = roundup(b->argidx, sizeof(u64));
 
 	BUG_ON(preemptible());
-	BUG_ON(b->argidx > MC_ARGS);
+	BUG_ON(b->argidx >= MC_ARGS);
 
 	if (b->mcidx == MC_BATCH ||
-	    (argidx + args) > MC_ARGS) {
+	    (argidx + args) >= MC_ARGS) {
 		mc_stats_flush(b->mcidx == MC_BATCH ? FL_SLOTS : FL_ARGS);
 		xen_mc_flush();
 		argidx = roundup(b->argidx, sizeof(u64));
@@ -206,7 +206,7 @@ struct multicall_space __xen_mc_entry(size_t args)
 	ret.args = &b->args[argidx];
 	b->argidx = argidx + args;
 
-	BUG_ON(b->argidx > MC_ARGS);
+	BUG_ON(b->argidx >= MC_ARGS);
 	return ret;
 }
 
@@ -216,7 +216,7 @@ struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
 	struct multicall_space ret = { NULL, NULL };
 
 	BUG_ON(preemptible());
-	BUG_ON(b->argidx > MC_ARGS);
+	BUG_ON(b->argidx >= MC_ARGS);
 
 	if (b->mcidx == 0)
 		return ret;
@@ -224,14 +224,14 @@ struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
 	if (b->entries[b->mcidx - 1].op != op)
 		return ret;
 
-	if ((b->argidx + size) > MC_ARGS)
+	if ((b->argidx + size) >= MC_ARGS)
 		return ret;
 
 	ret.mc = &b->entries[b->mcidx - 1];
 	ret.args = &b->args[b->argidx];
 	b->argidx += size;
 
-	BUG_ON(b->argidx > MC_ARGS);
+	BUG_ON(b->argidx >= MC_ARGS);
 	return ret;
 }
 
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 3ff822b48145..553da68bd510 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -626,6 +626,9 @@ int xen_allocate_pirq_gsi(unsigned gsi)
  *
  * Note: We don't assign an event channel until the irq actually started
  * up.  Return an existing irq if we've already got one for the gsi.
+ *
+ * Shareable implies level triggered, not shareable implies edge
+ * triggered here.
  */
 int xen_bind_pirq_gsi_to_irq(unsigned gsi,
 			     unsigned pirq, int shareable, char *name)
@@ -664,16 +667,13 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
 
 	pirq_query_unmask(irq);
 	/* We try to use the handler with the appropriate semantic for the
-	 * type of interrupt: if the interrupt doesn't need an eoi
-	 * (pirq_needs_eoi returns false), we treat it like an edge
-	 * triggered interrupt so we use handle_edge_irq.
-	 * As a matter of fact this only happens when the corresponding
-	 * physical interrupt is edge triggered or an msi.
+	 * type of interrupt: if the interrupt is an edge triggered
+	 * interrupt we use handle_edge_irq.
 	 *
-	 * On the other hand if the interrupt needs an eoi (pirq_needs_eoi
-	 * returns true) we treat it like a level triggered interrupt so we
-	 * use handle_fasteoi_irq like the native code does for this kind of
+	 * On the other hand if the interrupt is level triggered we use
+	 * handle_fasteoi_irq like the native code does for this kind of
 	 * interrupts.
+	 *
 	 * Depending on the Xen version, pirq_needs_eoi might return true
 	 * not only for level triggered interrupts but for edge triggered
 	 * interrupts too. In any case Xen always honors the eoi mechanism,
@@ -681,7 +681,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
 	 * hasn't received an eoi yet. Therefore using the fasteoi handler
 	 * is the right choice either way.
 	 */
-	if (pirq_needs_eoi(irq))
+	if (shareable)
 		irq_set_chip_and_handler_name(irq, &xen_pirq_chip,
 				handle_fasteoi_irq, name);
 	else