It calls iommufd_backend_get_device_info() to get host IOMMU
related information and translate it into HostIOMMUDeviceCaps
for query with .get_cap().

Introduce macro VTD_MGAW_FROM_CAP to get MGAW which equals to
(aw_bits - 1).

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 include/hw/i386/intel_iommu.h |  1 +
 hw/vfio/iommufd.c             | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index 7fa0a695c8..7d694b0813 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -47,6 +47,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(IntelIOMMUState, INTEL_IOMMU_DEVICE)
 #define VTD_HOST_AW_48BIT           48
 #define VTD_HOST_ADDRESS_WIDTH      VTD_HOST_AW_39BIT
 #define VTD_HAW_MASK(aw)            ((1ULL << (aw)) - 1)
+#define VTD_MGAW_FROM_CAP(cap)      ((cap >> 16) & 0x3fULL)
 
 #define DMAR_REPORT_F_INTR          (1)
 
diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
index e4a507d55c..9d2e95e20e 100644
--- a/hw/vfio/iommufd.c
+++ b/hw/vfio/iommufd.c
@@ -25,6 +25,7 @@
 #include "qemu/cutils.h"
 #include "qemu/chardev_open.h"
 #include "pci.h"
+#include "hw/i386/intel_iommu_internal.h"
 
 static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
                             ram_addr_t size, void *vaddr, bool readonly)
@@ -619,6 +620,41 @@ static void vfio_iommu_iommufd_class_init(ObjectClass *klass, void *data)
     vioc->pci_hot_reset = iommufd_cdev_pci_hot_reset;
 };
 
+static bool hiod_iommufd_vfio_realize(HostIOMMUDevice *hiod, void *opaque,
+                                      Error **errp)
+{
+    VFIODevice *vdev = opaque;
+    HostIOMMUDeviceCaps *caps = &hiod->caps;
+    enum iommu_hw_info_type type;
+    union {
+        struct iommu_hw_info_vtd vtd;
+    } data;
+
+    if (!iommufd_backend_get_device_info(vdev->iommufd, vdev->devid,
+                                         &type, &data, sizeof(data), errp)) {
+        return false;
+    }
+
+    caps->type = type;
+
+    switch (type) {
+    case IOMMU_HW_INFO_TYPE_INTEL_VTD:
+        caps->aw_bits = VTD_MGAW_FROM_CAP(data.vtd.cap_reg) + 1;
+        break;
+    case IOMMU_HW_INFO_TYPE_NONE:
+        break;
+    }
+
+    return true;
+}
+
+static void hiod_iommufd_vfio_class_init(ObjectClass *oc, void *data)
+{
+    HostIOMMUDeviceClass *hiodc = HOST_IOMMU_DEVICE_CLASS(oc);
+
+    hiodc->realize = hiod_iommufd_vfio_realize;
+};
+
 static const TypeInfo types[] = {
     {
         .name = TYPE_VFIO_IOMMU_IOMMUFD,
@@ -627,6 +663,7 @@ static const TypeInfo types[] = {
     }, {
         .name = TYPE_HOST_IOMMU_DEVICE_IOMMUFD_VFIO,
         .parent = TYPE_HOST_IOMMU_DEVICE_IOMMUFD,
+        .class_init = hiod_iommufd_vfio_class_init,
     }
 };
 
-- 
2.34.1