diff --git a/xen/drivers/passthrough/amd/iommu_guest.c b/xen/drivers/passthrough/amd/iommu_guest.c
index 952600a9c6..477de208bf 100644
--- a/xen/drivers/passthrough/amd/iommu_guest.c
+++ b/xen/drivers/passthrough/amd/iommu_guest.c
@@ -424,12 +424,17 @@ static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
                                         sizeof(dev_entry_t), gbdf);
     ASSERT(mfn_valid(dte_mfn));
 
+    /* Read guest dte information */
     dte_base = map_domain_page(dte_mfn);
 
     gdte = dte_base + gbdf % (PAGE_SIZE / sizeof(dev_entry_t));
 
     gdom_id  = get_domid_from_dte(gdte);
     gcr3_gfn = get_guest_cr3_from_dte(gdte);
+    glx      = get_glx_from_dte(gdte);
+    gv       = get_gv_from_dte(gdte);
+
+    unmap_domain_page(dte_base);
 
     /* Do not update host dte before gcr3 has been set */
     if ( gcr3_gfn == 0 )
@@ -440,7 +445,6 @@ static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
 
     ASSERT(mfn_valid(gcr3_mfn));
 
-    /* Read guest dte information */
     iommu = find_iommu_for_device(0, mbdf);
     if ( !iommu )
     {
@@ -449,11 +453,6 @@ static int do_invalidate_dte(struct domain *d, cmd_entry_t *cmd)
         return -ENODEV;
     }
 
-    glx = get_glx_from_dte(gdte);
-    gv = get_gv_from_dte(gdte);
-
-    unmap_domain_page(dte_base);
-
     /* Setup host device entry */
     hdom_id = host_domid(d, gdom_id);
     req_id = get_dma_requestor_id(iommu->seg, mbdf);