diff --git a/xen/drivers/passthrough/amd/iommu_intr.c b/xen/drivers/passthrough/amd/iommu_intr.c
index 7fc796dec2..f07fd9e3d9 100644
--- a/xen/drivers/passthrough/amd/iommu_intr.c
+++ b/xen/drivers/passthrough/amd/iommu_intr.c
@@ -649,6 +649,19 @@ bool __init cf_check iov_supports_xt(void)
     if ( !iommu_enable || !iommu_intremap )
         return false;
 
+    if ( unlikely(!cpu_has_cx16) )
+    {
+        AMD_IOMMU_ERROR("no CMPXCHG16B support, disabling IOMMU\n");
+        /*
+         * Disable IOMMU support at once: there's no reason to check for CX16
+         * yet again when attempting to initialize IOMMU DMA remapping
+         * functionality or interrupt remapping without x2APIC support.
+         */
+        iommu_enable = false;
+        iommu_intremap = iommu_intremap_off;
+        return false;
+    }
+
     if ( amd_iommu_prepare(true) )
         return false;
 
diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c
index 73dcc4a2dd..f96f59440b 100644
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -309,6 +309,12 @@ static int __init cf_check iov_detect(void)
     if ( !iommu_enable && !iommu_intremap )
         return 0;
 
+    if ( unlikely(!cpu_has_cx16) )
+    {
+        AMD_IOMMU_ERROR("no CMPXCHG16B support, disabling IOMMU\n");
+        return -ENODEV;
+    }
+
     if ( (init_done ? amd_iommu_init_late()
                     : amd_iommu_init(false)) != 0 )
     {
diff --git a/xen/drivers/passthrough/vtd/intremap.c b/xen/drivers/passthrough/vtd/intremap.c
index c504852eb8..233db5cb64 100644
--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -150,6 +150,19 @@ bool __init cf_check intel_iommu_supports_eim(void)
     if ( !iommu_qinval || !iommu_intremap || list_empty(&acpi_drhd_units) )
         return false;
 
+    if ( unlikely(!cpu_has_cx16) )
+    {
+        printk(XENLOG_ERR VTDPREFIX "no CMPXCHG16B support, disabling IOMMU\n");
+        /*
+         * Disable IOMMU support at once: there's no reason to check for CX16
+         * yet again when attempting to initialize IOMMU DMA remapping
+         * functionality or interrupt remapping without x2APIC support.
+         */
+        iommu_enable = false;
+        iommu_intremap = iommu_intremap_off;
+        return false;
+    }
+
     /* We MUST have a DRHD unit for each IOAPIC. */
     for ( apic = 0; apic < nr_ioapics; apic++ )
         if ( !ioapic_to_drhd(IO_APIC_ID(apic)) )
diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index 27a4d16401..3daedc4f55 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2633,6 +2633,13 @@ static int __init cf_check vtd_setup(void)
     int ret;
     bool reg_inval_supported = true;
 
+    if ( unlikely(!cpu_has_cx16) )
+    {
+        printk(XENLOG_ERR VTDPREFIX "no CMPXCHG16B support, disabling IOMMU\n");
+        ret = -ENODEV;
+        goto error;
+    }
+
     if ( list_empty(&acpi_drhd_units) )
     {
         ret = -ENODEV;