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[Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page

The Xen interface is always using 4KB page. This means that a Linux page
may be split across multiple Xen page when the page granularity is not
the same.

This helper will break down a Linux page into 4KB chunk and call the
helper on each of them.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
    Changes in v2:
        - Patch added
 include/xen/page.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/xen/page.h b/include/xen/page.h
index 8ebd37b..b1f7722 100644
--- a/include/xen/page.h
+++ b/include/xen/page.h
@@ -39,4 +39,24 @@ struct xen_memory_region 
 extern unsigned long xen_released_pages;
+typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data);
+/* Break down the page in 4KB granularity and call fn foreach xen pfn */
+static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn,
+                                   void *data)
+       unsigned long pfn = xen_page_to_pfn(page);
+       int i;
+       int ret;
+       for (i = 0; i < XEN_PFN_PER_PAGE; i++, pfn++) {
+               ret = fn(page, pfn, data);
+               if (ret)
+                       return ret;
+       }
+       return ret;
 #endif /* _XEN_PAGE_H */

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