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[Xen-devel] [PATCH v3 05/20] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one

Many PV drivers contain the idiom:

pfn = page_to_gfn(...) /* Or similar */

Replace it by a new helper. Note that when Linux is using a different
page granularity than Xen, the helper only gives access to the first 4KB

This is useful where drivers are allocating a full Linux page for each

Also include xen/interface/grant_table.h rather than xen/grant_table.h in
asm/page.h for x86 to fix a compilation issue [1]. Only the former is
useful in order to get the structure definition.

[1] Interdependency between asm/page.h and xen/grant_table.h which result
to page_mfn not being defined when necessary.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Reviewed-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

    Changes in v3:
        - Rename gnttab_page_grant_foreign_access_ref into
        - Fix typo in the commit message
        - s/mfn/gfn based on the new naming
        - Add David and Stefano's reviewed-by

    Changes in v2:
        - Patch added
 include/xen/grant_table.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 2a8ebe8..1c1ddd9 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -131,6 +131,15 @@ void gnttab_cancel_free_callback(struct 
gnttab_free_callback *callback);
 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
                                     unsigned long frame, int readonly);
+/* Give access to the first 4K of the page */
+static inline void gnttab_page_grant_foreign_access_ref_one(
+       grant_ref_t ref, domid_t domid,
+       struct page *page, int readonly)
+       gnttab_grant_foreign_access_ref(ref, domid, xen_page_to_gfn(page),
+                                       readonly);
 void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid,
                                       unsigned long pfn);

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