xen/grant-table: Add an helper to iterate over a specific number of grants

With the 64KB page granularity support on ARM64, a Linux page may be
split accross multiple grant.

Currently we have the helper gnttab_foreach_grant_in_grant to break a
Linux page based on an offset and a len, but it doesn't fit when we only
have a number of grants in hand.

Introduce a new helper which take an array of Linux page and a number of
grant and will figure out the address of each grant.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 72d633962095eae623826c546bae69f7652bfc71..c49f79ed58c53353cbbf4dc34fa7dd5902388ea9 100644 (file)
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -802,6 +802,28 @@ void gnttab_foreach_grant_in_range(struct page *page,
 }
 EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);
 
+void gnttab_foreach_grant(struct page **pages,
+                         unsigned int nr_grefs,
+                         xen_grant_fn_t fn,
+                         void *data)
+{
+       unsigned int goffset = 0;
+       unsigned long xen_pfn = 0;
+       unsigned int i;
+
+       for (i = 0; i < nr_grefs; i++) {
+               if ((i % XEN_PFN_PER_PAGE) == 0) {
+                       xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
+                       goffset = 0;
+               }
+
+               fn(pfn_to_gfn(xen_pfn), goffset, XEN_PAGE_SIZE, data);
+
+               goffset += XEN_PAGE_SIZE;
+               xen_pfn++;
+       }
+}
+
 int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                    struct gnttab_map_grant_ref *kmap_ops,
                    struct page **pages, unsigned int count)

diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index e17a4b381a16c083b5b6a563b3d4eb732dcc731e..34b1379f9777d4e7969f3288a51305c0c8738c9d 100644 (file)
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -264,6 +264,12 @@ static inline void gnttab_for_one_grant(struct page *page, unsigned int offset,
        gnttab_foreach_grant_in_range(page, offset, len, fn, data);
 }
 
+/* Get @nr_grefs grants from an array of page and call fn for each grant */
+void gnttab_foreach_grant(struct page **pages,
+                         unsigned int nr_grefs,
+                         xen_grant_fn_t fn,
+                         void *data);
+
 /* Get the number of grant in a specified region
  *
  * start: Offset from the beginning of the first page