xen/grant: Introduce helpers to split a page into grant
Currently, a grant is always based on the Xen page granularity (i.e
4KB). When Linux is using a different page granularity, a single page
will be split between multiple grants.
The new helpers will be in charge of splitting the Linux page into grants
and call a function given by the caller on each grant.
Also provide an helper to count the number of grants within a given
contiguous region.
Note that the x86/include/asm/xen/page.h is now including
xen/interface/grant_table.h rather than xen/grant_table.h. It's
necessary because xen/grant_table.h depends on asm/xen/page.h and will
break the compilation. Furthermore, only definition in
interface/grant_table.h is required.
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.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 a4b702c9..dbeaa67 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -776,6 +776,32 @@
}
EXPORT_SYMBOL_GPL(gnttab_batch_copy);
+void gnttab_foreach_grant_in_range(struct page *page,
+ unsigned int offset,
+ unsigned int len,
+ xen_grant_fn_t fn,
+ void *data)
+{
+ unsigned int goffset;
+ unsigned int glen;
+ unsigned long xen_pfn;
+
+ len = min_t(unsigned int, PAGE_SIZE - offset, len);
+ goffset = xen_offset_in_page(offset);
+
+ xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(offset);
+
+ while (len) {
+ glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);
+ fn(pfn_to_gfn(xen_pfn), goffset, glen, data);
+
+ goffset = 0;
+ xen_pfn++;
+ len -= glen;
+ }
+}
+EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);
+
int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
struct gnttab_map_grant_ref *kmap_ops,
struct page **pages, unsigned int count)