The realize function populates the capabilities. For now only the
aw_bits caps is computed for legacy backend.

Introduce a helper function vfio_device_get_aw_bits() which calls
range_get_last_bit() to get host aw_bits and package it in
HostIOMMUDeviceCaps for query with .get_cap(). This helper will
also be used by iommufd backend.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 include/hw/vfio/vfio-common.h |  1 +
 hw/vfio/container.c           | 19 +++++++++++++++++++
 hw/vfio/helpers.c             | 17 +++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 56d1717211..105b8b7e80 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -289,4 +289,5 @@ bool vfio_device_get_name(VFIODevice *vbasedev, Error **errp);
 void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp);
 void vfio_device_init(VFIODevice *vbasedev, int type, VFIODeviceOps *ops,
                       DeviceState *dev, bool ram_discard);
+int vfio_device_get_aw_bits(VFIODevice *vdev);
 #endif /* HW_VFIO_VFIO_COMMON_H */
diff --git a/hw/vfio/container.c b/hw/vfio/container.c
index c4fca2dfca..2f62c13214 100644
--- a/hw/vfio/container.c
+++ b/hw/vfio/container.c
@@ -1136,6 +1136,24 @@ static void vfio_iommu_legacy_class_init(ObjectClass *klass, void *data)
     vioc->pci_hot_reset = vfio_legacy_pci_hot_reset;
 };
 
+static bool hiod_legacy_vfio_realize(HostIOMMUDevice *hiod, void *opaque,
+                                     Error **errp)
+{
+    VFIODevice *vdev = opaque;
+
+    hiod->name = g_strdup(vdev->name);
+    hiod->caps.aw_bits = vfio_device_get_aw_bits(vdev);
+
+    return true;
+}
+
+static void hiod_legacy_vfio_class_init(ObjectClass *oc, void *data)
+{
+    HostIOMMUDeviceClass *hioc = HOST_IOMMU_DEVICE_CLASS(oc);
+
+    hioc->realize = hiod_legacy_vfio_realize;
+};
+
 static const TypeInfo types[] = {
     {
         .name = TYPE_VFIO_IOMMU_LEGACY,
@@ -1144,6 +1162,7 @@ static const TypeInfo types[] = {
     }, {
         .name = TYPE_HOST_IOMMU_DEVICE_LEGACY_VFIO,
         .parent = TYPE_HOST_IOMMU_DEVICE,
+        .class_init = hiod_legacy_vfio_class_init,
     }
 };
 
diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
index 27ea26aa48..b14edd46ed 100644
--- a/hw/vfio/helpers.c
+++ b/hw/vfio/helpers.c
@@ -658,3 +658,20 @@ void vfio_device_init(VFIODevice *vbasedev, int type, VFIODeviceOps *ops,
 
     vbasedev->ram_block_discard_allowed = ram_discard;
 }
+
+int vfio_device_get_aw_bits(VFIODevice *vdev)
+{
+    /*
+     * iova_ranges is a sorted list. For old kernels that support
+     * VFIO but not support query of iova ranges, iova_ranges is NULL,
+     * in this case HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX(64) is returned.
+     */
+    GList *l = g_list_last(vdev->bcontainer->iova_ranges);
+
+    if (l) {
+        Range *range = l->data;
+        return range_get_last_bit(range) + 1;
+    }
+
+    return HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX;
+}
-- 
2.34.1