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[PATCH v5 05/22] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one

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  [PATCH v5 05/22] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one Julien Grall <julien.grall@citrix.com> - 2015-09-30 12:50 +0200
    Re: [PATCH v5 05/22] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one Julien Grall <julien.grall@citrix.com> - 2015-09-30 13:00 +0200

#1236124 — [PATCH v5 05/22] xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one

Many PV drivers contain the idiom:

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

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
grant.

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

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@linaro.org>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>

    Changes in v3:
        - Rename gnttab_page_grant_foreign_access_ref into
        gnttab_page_grant_foreign_access_ref_one
        - 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);
 
-- 
2.1.4

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#1236142

On 30/09/15 11:45, Julien Grall wrote:
> Many PV drivers contain the idiom:
> 
> pfn = page_to_gfn(...) /* Or similar */
> gnttab_grant_foreign_access_ref
> 
> 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
> grant.
> 
> This is useful where drivers are allocating a full Linux page for each
> grant.
> 
> 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@linaro.org>

Hmmm... this should be julien.grall@citrix.com. Still mixing up with my
old address.

I've fixed it in the branch associated to this series.

Regards,

-- 
Julien Grall
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