[Xen-devel] [PATCH 3/6] xen/grant-table: Support mappings required by blkback

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

Add support for mappings without GNTMAP_contains_pte. This was not
supported because the unmap operation assumed that this flag was being
used; adding a parameter to the unmap operation to allow the PTE
clearing to be disabled is sufficient to make unmap capable of
supporting either mapping type.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 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__ */
-- 
1.7.7.4


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