[PATCH v4 05/20] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one

From: Julien Grall
Date: Mon Sep 07 2015 - 11:36:45 EST

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 05b5b08..e17a4b3 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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