[PATCH 03/12] xen/grant-table: Support mappings required by blkback

[Daniel De Graaf <dgdegra@tycho.nsa.gov>]

Allow mappings without GNTMAP_contains_pte and allow unmapping to
specify if the PTEs should be cleared.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
---
 drivers/xen/gntdev.c      |    3 ++-
 drivers/xen/grant-table.c |   23 ++++-------------------
 include/xen/grant_table.h |    2 +-
 3 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index afca14d..65bff07 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -312,7 +312,8 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
 		}
 	}
 
-	err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset, pages);
+	err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset,
+	                        pages, true);
 	if (err)
 		return err;
 
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index bf1c094..a02d139 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -472,24 +472,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 				(map_ops[i].host_addr & ~PAGE_MASK));
 			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;
+			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 		}
-		ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
+		ret = m2p_add_override(mfn, pages[i], kmap_ops ? &kmap_ops[i] : NULL);
 		if (ret)
 			return ret;
 	}
@@ -499,7 +484,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-		struct page **pages, unsigned int count)
+		struct page **pages, unsigned int count, bool clear_pte)
 {
 	int i, ret;
 
@@ -511,7 +496,7 @@ 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], true /* clear the PTE */);
+		ret = m2p_remove_override(pages[i], clear_pte);
 		if (ret)
 			return ret;
 	}
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 11e2dfc..37da54d 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -158,6 +158,6 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 			struct gnttab_map_grant_ref *kmap_ops,
 		    struct page **pages, unsigned int count);
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-		      struct page **pages, unsigned int count);
+		      struct page **pages, unsigned int count, bool clear_pte);
 
 #endif /* __ASM_GNTTAB_H__ */
-- 
1.7.7.3