diff --git a/xen/arch/arm/domctl.c b/xen/arch/arm/domctl.c
index c10f568aad..20691528a6 100644
--- a/xen/arch/arm/domctl.c
+++ b/xen/arch/arm/domctl.c
@@ -52,16 +52,16 @@ long arch_do_domctl(struct xen_domctl *domctl, struct domain *d,
     {
     case XEN_DOMCTL_cacheflush:
     {
-        unsigned long s = domctl->u.cacheflush.start_pfn;
-        unsigned long e = s + domctl->u.cacheflush.nr_pfns;
+        gfn_t s = _gfn(domctl->u.cacheflush.start_pfn);
+        gfn_t e = gfn_add(s, domctl->u.cacheflush.nr_pfns);
 
         if ( domctl->u.cacheflush.nr_pfns > (1U<<MAX_ORDER) )
             return -EINVAL;
 
-        if ( e < s )
+        if ( gfn_x(e) < gfn_x(s) )
             return -EINVAL;
 
-        return p2m_cache_flush_range(d, _gfn(s), _gfn(e));
+        return p2m_cache_flush_range(d, s, e);
     }
     case XEN_DOMCTL_bind_pt_irq:
     {