1 files changed, 24 insertions, 7 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 3745a318defc..fd725cde6ad1 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -466,13 +466,30 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                 if (map_ops[i].status)
                         continue;
 
-                /* m2p override only supported for GNTMAP_contains_pte mappings */
-                if (!(map_ops[i].flags & GNTMAP_contains_pte))
-                        continue;
-                pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
+                if (map_ops[i].flags & GNTMAP_contains_pte) {
+                        pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
                                 (map_ops[i].host_addr & ~PAGE_MASK));
-                mfn = pte_mfn(*pte);
-                ret = m2p_add_override(mfn, pages[i]);
+                        mfn = pte_mfn(*pte);
+                } else {
+                        /* If you really wanted to do this:
+                         * mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
+                         *
+                         * The reason we do not implement it is b/c on the
+                         * unmap path (gnttab_unmap_refs) we have no means of
+                         * checking whether the page is !GNTMAP_contains_pte.
+                         *
+                         * That is without some extra data-structure to carry
+                         * the struct page, bool clear_pte, and list_head next
+                         * tuples and deal with allocation/delallocation, etc.
+                         *
+                         * The users of this API set the GNTMAP_contains_pte
+                         * flag so lets just return not supported until it
+                         * becomes neccessary to implement.
+                         */
+                        return -EOPNOTSUPP;
+                }
+                ret = m2p_add_override(mfn, pages[i],
+                                       map_ops[i].flags & GNTMAP_contains_pte);
                 if (ret)
                         return ret;
         }
@@ -494,7 +511,7 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
                 return ret;
 
         for (i = 0; i < count; i++) {
-                ret = m2p_remove_override(pages[i]);
+                ret = m2p_remove_override(pages[i], true /* clear the PTE */);
                 if (ret)
                         return ret;
         }