Having a way to figure out the region index (or bar) associated
with a memory region is helpful in various scenarios. For example,
this capability can be useful in retrieving the region info 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/region.c              | 14 ++++++++++++++
 include/hw/vfio/vfio-device.h | 10 ++++++++++
 2 files changed, 24 insertions(+)

diff --git a/hw/vfio/region.c b/hw/vfio/region.c
index ab39d77574..8943128dd2 100644
--- a/hw/vfio/region.c
+++ b/hw/vfio/region.c
@@ -461,3 +461,17 @@ void vfio_region_mmaps_set_enabled(VFIORegion *region, bool enabled)
     trace_vfio_region_mmaps_set_enabled(memory_region_name(region->mem),
                                         enabled);
 }
+
+int vfio_get_region_index_from_mr(MemoryRegion *mr)
+{
+    VFIORegion *region;
+
+    while (mr->container) {
+        if (mr->ops == &vfio_region_ops) {
+            region = mr->opaque;
+	    return region->nr;
+        }
+        mr = mr->container;
+    }
+    return -1;
+}
diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
index 828a31c006..596c7f5a10 100644
--- a/include/hw/vfio/vfio-device.h
+++ b/include/hw/vfio/vfio-device.h
@@ -308,6 +308,16 @@ bool vfio_device_has_region_cap(VFIODevice *vbasedev, int region, uint16_t cap_t
 
 int vfio_device_get_irq_info(VFIODevice *vbasedev, int index,
                                 struct vfio_irq_info *info);
+
+/**
+ * Return the region index associated with a given MemoryRegion. The index
+ * can be useful in retrieving region info.
+ *
+ * @mr: MemoryRegion to use
+ *
+ * Returns the region index or -1 on error.
+ */
+int vfio_get_region_index_from_mr(MemoryRegion *mr);
 #endif
 
 /* Returns 0 on success, or a negative errno. */
-- 
2.50.1