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/include/xen/grant_table.h b/include/xen/grant_table.h
index 4478f4b..05b5b08 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -45,8 +45,10 @@
#include <asm/xen/hypervisor.h>
#include <xen/features.h>
+#include <xen/page.h>
#include <linux/mm_types.h>
#include <linux/page-flags.h>
+#include <linux/kernel.h>
#define GNTTAB_RESERVED_XENSTORE 1
@@ -224,4 +226,44 @@
#endif
}
+/* Split Linux page in chunk of the size of the grant and call fn
+ *
+ * Parameters of fn:
+ * gfn: guest frame number
+ * offset: offset in the grant
+ * len: length of the data in the grant.
+ * data: internal information
+ */
+typedef void (*xen_grant_fn_t)(unsigned long gfn, unsigned int offset,
+ unsigned int len, void *data);
+
+void gnttab_foreach_grant_in_range(struct page *page,
+ unsigned int offset,
+ unsigned int len,
+ xen_grant_fn_t fn,
+ void *data);
+
+/* Helper to get to call fn only on the first "grant chunk" */
+static inline void gnttab_for_one_grant(struct page *page, unsigned int offset,
+ unsigned len, xen_grant_fn_t fn,
+ void *data)
+{
+ /* The first request is limited to the size of one grant */
+ len = min_t(unsigned int, XEN_PAGE_SIZE - (offset & ~XEN_PAGE_MASK),
+ len);
+
+ gnttab_foreach_grant_in_range(page, offset, len, fn, data);
+}
+
+/* Get the number of grant in a specified region
+ *
+ * start: Offset from the beginning of the first page
+ * len: total length of data (can cross multiple page)
+ */
+static inline unsigned int gnttab_count_grant(unsigned int start,
+ unsigned int len)
+{
+ return XEN_PFN_UP(xen_offset_in_page(start) + len);
+}
+
#endif /* __ASM_GNTTAB_H__ */