diff --git a/xen/drivers/passthrough/amd/iommu-defs.h b/xen/drivers/passthrough/amd/iommu-defs.h
index 0c97db2a32..8810e497b9 100644
--- a/xen/drivers/passthrough/amd/iommu-defs.h
+++ b/xen/drivers/passthrough/amd/iommu-defs.h
@@ -106,6 +106,7 @@ struct amd_iommu_dte {
     bool tv:1;
     unsigned int :5;
     unsigned int had:2;
+#define IOMMU_MAX_PT_LEVELS 6
     unsigned int paging_mode:3;
     uint64_t pt_root:40;
     bool ppr:1;
diff --git a/xen/drivers/passthrough/amd/iommu.h b/xen/drivers/passthrough/amd/iommu.h
index 79c6a5b5b0..1cddbb9f94 100644
--- a/xen/drivers/passthrough/amd/iommu.h
+++ b/xen/drivers/passthrough/amd/iommu.h
@@ -362,7 +362,7 @@ static inline int amd_iommu_get_paging_mode(unsigned long max_frames)
     while ( max_frames > PTE_PER_TABLE_SIZE )
     {
         max_frames = PTE_PER_TABLE_ALIGN(max_frames) >> PTE_PER_TABLE_SHIFT;
-        if ( ++level > 6 )
+        if ( ++level > IOMMU_MAX_PT_LEVELS )
             return -ENOMEM;
     }
 
diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c
index eb38c9a0bf..544c5bc2e4 100644
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -256,7 +256,7 @@ static int iommu_pde_from_dfn(struct domain *d, unsigned long dfn,
     table = hd->arch.root_table;
     level = hd->arch.paging_mode;
 
-    BUG_ON( table == NULL || level < 1 || level > 6 );
+    BUG_ON( table == NULL || level < 1 || level > IOMMU_MAX_PT_LEVELS );
 
     /*
      * A frame number past what the current page tables can represent can't