diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index 40619b25d4..b5a8f29568 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -55,7 +55,7 @@ static int vgic_v2_distr_mmio_read(struct vcpu *v, mmio_info_t *info)
         /* No secure world support for guests. */
         vgic_lock(v);
         *r = ( ((v->domain->max_vcpus - 1) << GICD_TYPE_CPUS_SHIFT) )
-            |( ((v->domain->arch.vgic.nr_spis / 32)) & GICD_TYPE_LINES );
+            | DIV_ROUND_UP(v->domain->arch.vgic.nr_spis, 32);
         vgic_unlock(v);
         return 1;
     case GICD_IIDR:
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 81fbb26adb..45a46c3b13 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -700,7 +700,7 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, mmio_info_t *info)
         if ( dabt.size != DABT_WORD ) goto bad_width;
         /* No secure world support for guests. */
         *r = ((ncpus - 1) << GICD_TYPE_CPUS_SHIFT |
-              ((v->domain->arch.vgic.nr_spis / 32) & GICD_TYPE_LINES));
+              DIV_ROUND_UP(v->domain->arch.vgic.nr_spis, 32));
 
         *r |= (irq_bits - 1) << GICD_TYPE_ID_BITS_SHIFT;