[PATCH v12 06/10] vfio/region: Add a helper to get VFIO region from memory region

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

Having a way to get the VFIO region associated with a memory region
is helpful in various scenarios. For example, this capability can
be useful in retrieving the region info such as index and offset
needed for mapping a part of a VFIO region or creating a dmabuf.

Cc: Alex Williamson <alex@shazbot.org>
Cc: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 hw/vfio/vfio-region.h | 10 ++++++++++
 hw/vfio/region.c      | 11 +++++++++++
 2 files changed, 21 insertions(+)

diff --git a/hw/vfio/vfio-region.h b/hw/vfio/vfio-region.h
index 9b21d4ee5b..3dd47f77f6 100644
--- a/hw/vfio/vfio-region.h
+++ b/hw/vfio/vfio-region.h
@@ -45,4 +45,14 @@ void vfio_region_unmap(VFIORegion *region);
 void vfio_region_exit(VFIORegion *region);
 void vfio_region_finalize(VFIORegion *region);
 
+/**
+ * Return the VFIO region associated with a given MemoryRegion. This can
+ * be useful in retrieving region info such as index and offset.
+ *
+ * @mr: MemoryRegion to use
+ *
+ * Returns the region or NULL on error.
+ */
+void *vfio_get_region_from_mr(MemoryRegion *mr);
+
 #endif /* HW_VFIO_REGION_H */
diff --git a/hw/vfio/region.c b/hw/vfio/region.c
index 47fdc2df34..9d7ac339c9 100644
--- a/hw/vfio/region.c
+++ b/hw/vfio/region.c
@@ -539,3 +539,14 @@ void vfio_region_mmaps_set_enabled(VFIORegion *region, bool enabled)
     trace_vfio_region_mmaps_set_enabled(memory_region_name(region->mem),
                                         enabled);
 }
+
+void *vfio_get_region_from_mr(MemoryRegion *mr)
+{
+    while (mr->container) {
+        if (mr->ops == &vfio_region_ops) {
+            return mr->opaque;
+        }
+        mr = mr->container;
+    }
+    return NULL;
+}
-- 
2.53.0