diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c
index 330f9ce386..4a633ca940 100644
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -300,6 +300,8 @@ static void __hwdom_init amd_iommu_hwdom_init(struct domain *d)
                                         IOMMU_MMIO_REGION_LENGTH - 1)) )
             BUG();
 
+    /* Make sure workarounds are applied (if needed) before adding devices. */
+    arch_iommu_hwdom_init(d);
     setup_hwdom_pci_devices(d, amd_iommu_add_device);
 }
 
diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c
index 43ece42a50..8f91807b1b 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -2736,6 +2736,8 @@ static void __hwdom_init arm_smmu_iommu_hwdom_init(struct domain *d)
 		printk(XENLOG_WARNING
 		"map-reserved dom0-iommu option is not supported on ARM\n");
 	iommu_hwdom_reserved = 0;
+
+	arch_iommu_hwdom_init(d);
 }
 
 static void arm_smmu_iommu_domain_teardown(struct domain *d)
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index ee3f523fdf..ae6cf2f0ff 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -238,16 +238,6 @@ void __hwdom_init iommu_hwdom_init(struct domain *d)
     }
 
     hd->platform_ops->hwdom_init(d);
-
-    ASSERT(iommu_hwdom_inclusive != -1 && iommu_hwdom_inclusive != -1);
-    if ( iommu_hwdom_inclusive && !is_pv_domain(d) )
-    {
-        printk(XENLOG_WARNING
-               "IOMMU inclusive mappings are only supported on PV Dom0\n");
-        iommu_hwdom_inclusive = 0;
-    }
-
-    arch_iommu_hwdom_init(d);
 }
 
 void iommu_teardown(struct domain *d)
diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index adc70f205a..bb422ec58c 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1313,6 +1313,8 @@ static void __hwdom_init intel_iommu_hwdom_init(struct domain *d)
 
     setup_hwdom_pci_devices(d, setup_hwdom_device);
     setup_hwdom_rmrr(d);
+    /* Make sure workarounds are applied before enabling the IOMMU(s). */
+    arch_iommu_hwdom_init(d);
 
     if ( iommu_flush_all() )
         printk(XENLOG_WARNING VTDPREFIX
diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c
index 47a078272a..b7c8b5be41 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -210,6 +210,14 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
 
     BUG_ON(!is_hardware_domain(d));
 
+    ASSERT(iommu_hwdom_inclusive != -1 && iommu_hwdom_inclusive != -1);
+    if ( iommu_hwdom_inclusive && !is_pv_domain(d) )
+    {
+        printk(XENLOG_WARNING
+               "IOMMU inclusive mappings are only supported on PV Dom0\n");
+        iommu_hwdom_inclusive = 0;
+    }
+
     if ( iommu_hwdom_passthrough )
         return;