diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 8de9d01138..d5f38f225e 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -2044,6 +2044,8 @@ void asmlinkage __init noreturn __start_xen(void)
     if ( ret < 0 )
         panic("Error %d setting up IRQ data\n", ret);
 
+    bound_extra_guest_irqs();
+
     console_init_irq();
 
     init_IRQ();
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 35b11f6072..0ced34aaa6 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1164,6 +1164,26 @@ struct domain *domain_create(domid_t domid,
     return ERR_PTR(err);
 }
 
+#ifdef CONFIG_HAS_PIRQ
+/* Bound-check values passed via "extra_guest_irqs=", once nr_irqs is known. */
+void __init bound_extra_guest_irqs(void)
+{
+    unsigned int n = max(arch_hwdom_irqs(dom_xen), nr_static_irqs);
+
+    if ( extra_hwdom_irqs > n - nr_static_irqs )
+    {
+        extra_hwdom_irqs = n - nr_static_irqs;
+        printk(XENLOG_WARNING "hwdom IRQs bounded to %u\n", n);
+    }
+    if ( extra_domU_irqs >
+         max(DEFAULT_EXTRA_DOMU_IRQS, n - nr_static_irqs) )
+    {
+        extra_domU_irqs = n - nr_static_irqs;
+        printk(XENLOG_WARNING "domU IRQs bounded to %u\n", n);
+    }
+}
+#endif
+
 void __init setup_system_domains(void)
 {
     /*
@@ -1177,25 +1197,6 @@ void __init setup_system_domains(void)
     if ( IS_ERR(dom_xen) )
         panic("Failed to create d[XEN]: %ld\n", PTR_ERR(dom_xen));
 
-#ifdef CONFIG_HAS_PIRQ
-    /* Bound-check values passed via "extra_guest_irqs=". */
-    {
-        unsigned int n = max(arch_hwdom_irqs(dom_xen), nr_static_irqs);
-
-        if ( extra_hwdom_irqs > n - nr_static_irqs )
-        {
-            extra_hwdom_irqs = n - nr_static_irqs;
-            printk(XENLOG_WARNING "hwdom IRQs bounded to %u\n", n);
-        }
-        if ( extra_domU_irqs >
-             max(DEFAULT_EXTRA_DOMU_IRQS, n - nr_static_irqs) )
-        {
-            extra_domU_irqs = n - nr_static_irqs;
-            printk(XENLOG_WARNING "domU IRQs bounded to %u\n", n);
-        }
-    }
-#endif
-
     /*
      * Initialise our DOMID_IO domain.
      * This domain owns I/O pages that are within the range of the page_info
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index 313bb047cc..73d5975eb7 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -43,6 +43,9 @@ int vcpu_reset(struct vcpu *v);
 int vcpu_up(struct vcpu *v);
 
 void setup_system_domains(void);
+#ifdef CONFIG_HAS_PIRQ
+void bound_extra_guest_irqs(void);
+#endif
 
 struct xen_domctl_getdomaininfo;
 void getdomaininfo(struct domain *d, struct xen_domctl_getdomaininfo *info);