[Xen-devel] [PATCH 4/7] minios: add gnttab_find_grant_of_page

[Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Needed to implement minios_gntshr_munmap without introducing additional
mapping (frame->gref).

Signed-off-by: Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
 extras/mini-os/gnttab.c         | 23 +++++++++++++++++++++++
 extras/mini-os/include/gnttab.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/extras/mini-os/gnttab.c b/extras/mini-os/gnttab.c
index 2f1b3d7..ec32e69 100644
--- a/extras/mini-os/gnttab.c
+++ b/extras/mini-os/gnttab.c
@@ -157,6 +157,29 @@ gnttab_alloc_and_grant(void **map)
     return gref;
 }
 
+/* This function is used by gnttab_munmap call. It is rather rare to call it -
+ * mostly at sthudown, so save memory at price of efficiency */
+grant_ref_t
+gnttab_find_grant_of_page(void *map)
+{
+    unsigned long flags;
+    int i, mfn;
+    grant_ref_t ref = 0;
+
+    mfn = virt_to_mfn(map);
+    local_irq_save(flags);
+    for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++) {
+        if (!gnttab_table[i].flags)
+            continue;
+        if (gnttab_table[i].frame == mfn) {
+            ref = i;
+            break;
+        }
+    }
+    local_irq_restore(flags);
+    return ref;
+}
+
 static const char * const gnttabop_error_msgs[] = GNTTABOP_error_msgs;
 
 const char *
diff --git a/extras/mini-os/include/gnttab.h b/extras/mini-os/include/gnttab.h
index acd6c39..fb69daf 100644
--- a/extras/mini-os/include/gnttab.h
+++ b/extras/mini-os/include/gnttab.h
@@ -10,6 +10,7 @@ grant_ref_t gnttab_grant_access(domid_t domid, unsigned long 
frame,
 grant_ref_t gnttab_grant_transfer(domid_t domid, unsigned long pfn);
 unsigned long gnttab_end_transfer(grant_ref_t gref);
 int gnttab_end_access(grant_ref_t ref);
+grant_ref_t gnttab_find_grant_of_page(void *map);
 const char *gnttabop_error(int16_t status);
 void fini_gnttab(void);
 
-- 
1.8.1.4


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