[PATCH 2/4] xen: introduce grant_map_exists

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Check whether an mfn has been granted to a given domain on a target
grant table.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: jbeulich@suse.com
CC: tim@xen.org
---
 xen/common/grant_table.c      |   32 ++++++++++++++++++++++++++++++++
 xen/include/xen/grant_table.h |    4 ++++
 2 files changed, 36 insertions(+)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 23266c3..e1dc330 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -484,6 +484,38 @@ static int _set_status(unsigned gt_version,
         return _set_status_v2(domid, readonly, mapflag, shah, act, status);
 }
 
+bool_t grant_map_exists(struct domain *ld,
+                        struct grant_table *rgt,
+                        unsigned long mfn)
+{
+    struct active_grant_entry *act;
+    grant_ref_t ref;
+    bool_t ret = 0;
+
+    spin_lock(&rgt->lock);
+
+    for ( ref = 0; ref != nr_grant_entries(rgt); ref++ )
+    {
+        act = &active_entry(rgt, ref);
+
+        if ( !act->pin )
+            continue;
+
+        if ( act->domid != ld->domain_id )
+            continue;
+
+        if ( act->frame != mfn )
+            continue;
+        
+        ret = 1;
+        break;
+    }
+
+    spin_unlock(&rgt->lock);
+
+    return ret;
+}
+
 static void mapcount(
     struct grant_table *lgt, struct domain *rd, unsigned long mfn,
     unsigned int *wrc, unsigned int *rdc)
diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index 5941191..2df390f 100644
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -97,6 +97,10 @@ int grant_table_create(
 void grant_table_destroy(
     struct domain *d);
 
+bool_t grant_map_exists(struct domain *ld,
+                        struct grant_table *rgt,
+                        unsigned long mfn);
+
 /* Domain death release of granted mappings of other domains' memory. */
 void
 gnttab_release_mappings(
-- 
1.7.10.4