diff -r a2a8089b1ffb xen/drivers/passthrough/amd/iommu_guest.c
--- a/xen/drivers/passthrough/amd/iommu_guest.c	Tue Jan 24 16:46:17 2012 +0000
+++ b/xen/drivers/passthrough/amd/iommu_guest.c	Thu Jan 26 11:50:02 2012 +0100
@@ -805,6 +805,9 @@ int guest_iommu_set_base(struct domain *
     p2m_type_t t;
     struct guest_iommu *iommu = domain_iommu(d);
 
+    if ( !is_hvm_domain(d) || !iommu_enabled || !iommuv2_enabled )
+        return 0;
+
     if ( !iommu )
         return -EACCES;
 
@@ -867,7 +870,7 @@ int guest_iommu_init(struct domain* d)
     struct guest_iommu *iommu;
     struct hvm_iommu *hd  = domain_hvm_iommu(d);
 
-    if ( !is_hvm_domain(d) )
+    if ( !is_hvm_domain(d) || !iommu_enabled || !iommuv2_enabled )
         return 0;
 
     iommu = xzalloc(struct guest_iommu);
@@ -893,7 +896,7 @@ void guest_iommu_destroy(struct domain *
 {
     struct guest_iommu *iommu;
 
-    if ( !is_hvm_domain(d) )
+    if ( !is_hvm_domain(d) || !iommu_enabled || !iommuv2_enabled )
         return;
 
     iommu = domain_iommu(d);
diff -r a2a8089b1ffb xen/drivers/passthrough/amd/iommu_init.c
--- a/xen/drivers/passthrough/amd/iommu_init.c	Tue Jan 24 16:46:17 2012 +0000
+++ b/xen/drivers/passthrough/amd/iommu_init.c	Thu Jan 26 11:50:02 2012 +0100
@@ -38,6 +38,7 @@ unsigned short ivrs_bdf_entries;
 static struct radix_tree_root ivrs_maps;
 struct list_head amd_iommu_head;
 struct table_struct device_table;
+bool_t iommuv2_enabled = 0;
 
 static int iommu_has_ht_flag(struct amd_iommu *iommu, u8 mask)
 {
@@ -887,6 +888,9 @@ static int __init amd_iommu_init_one(str
 
     get_iommu_features(iommu);
 
+    if ( iommu->features )
+        iommuv2_enabled = 1;
+
     if ( allocate_cmd_buffer(iommu) == NULL )
         goto error_out;
 
@@ -950,6 +954,7 @@ static void __init amd_iommu_init_cleanu
     iommu_enabled = 0;
     iommu_passthrough = 0;
     iommu_intremap = 0;
+    iommuv2_enabled = 0;
 }
 
 /*
diff -r a2a8089b1ffb xen/include/asm-x86/amd-iommu.h
--- a/xen/include/asm-x86/amd-iommu.h	Tue Jan 24 16:46:17 2012 +0000
+++ b/xen/include/asm-x86/amd-iommu.h	Thu Jan 26 11:50:02 2012 +0100
@@ -182,4 +182,6 @@ struct guest_iommu {
     struct guest_iommu_msi  msi;
 };
 
+extern bool_t iommuv2_enabled;
+
 #endif /* _ASM_X86_64_AMD_IOMMU_H */