Currently the default input range can extend to 64 bits. On x86,
when the virtio-iommu protects vfio devices, the physical iommu
may support only 39 bits. Let's set the default to 39, as done
for the intel-iommu. We introduce a new compat to make sure older
pc_q35 machine types still use 64 bits. On ARM we keep 64b as
the default input address width. Of course if aw-bits is set
from the command line, the default is overriden.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/arm/virt.c            |  6 ++++++
 hw/i386/pc.c             | 10 +++++++++-
 hw/virtio/virtio-iommu.c |  2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 2793121cb4..a27fe13c73 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2715,10 +2715,16 @@ static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MD_PCI)) {
         virtio_md_pci_pre_plug(VIRTIO_MD_PCI(dev), MACHINE(hotplug_dev), errp);
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
+        uint8_t aw_bits = object_property_get_uint(OBJECT(dev),
+                                                   "aw-bits", NULL);
         hwaddr db_start = 0, db_end = 0;
         QList *reserved_regions;
         char *resv_prop_str;
 
+        if (!aw_bits) {
+            qdev_prop_set_uint8(dev, "aw-bits", 64);
+        }
+
         if (vms->iommu != VIRT_IOMMU_NONE) {
             error_setg(errp, "virt machine does not support multiple IOMMUs");
             return;
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 496498df3a..a8dbc99946 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -78,7 +78,9 @@
     { "qemu64-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },\
     { "athlon-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },
 
-GlobalProperty pc_compat_8_2[] = {};
+GlobalProperty pc_compat_8_2[] = {
+    { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "64" },
+};
 const size_t pc_compat_8_2_len = G_N_ELEMENTS(pc_compat_8_2);
 
 GlobalProperty pc_compat_8_1[] = {};
@@ -1458,6 +1460,8 @@ static void pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MD_PCI)) {
         virtio_md_pci_pre_plug(VIRTIO_MD_PCI(dev), MACHINE(hotplug_dev), errp);
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
+        uint8_t aw_bits = object_property_get_uint(OBJECT(dev),
+                                                   "aw-bits", NULL);
         /* Declare the APIC range as the reserved MSI region */
         char *resv_prop_str = g_strdup_printf("0xfee00000:0xfeefffff:%d",
                                               VIRTIO_IOMMU_RESV_MEM_T_MSI);
@@ -1466,6 +1470,10 @@ static void pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
         qlist_append_str(reserved_regions, resv_prop_str);
         qdev_prop_set_array(dev, "reserved-regions", reserved_regions);
 
+        if (!aw_bits) {
+            qdev_prop_set_uint8(dev, "aw-bits", 39);
+        }
+
         g_free(resv_prop_str);
     }
 
diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index e7f299e0c6..a7c268a01a 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -1526,7 +1526,7 @@ static Property virtio_iommu_properties[] = {
     DEFINE_PROP_LINK("primary-bus", VirtIOIOMMU, primary_bus,
                      TYPE_PCI_BUS, PCIBus *),
     DEFINE_PROP_BOOL("boot-bypass", VirtIOIOMMU, boot_bypass, true),
-    DEFINE_PROP_UINT8("aw-bits", VirtIOIOMMU, aw_bits, 64),
+    DEFINE_PROP_UINT8("aw-bits", VirtIOIOMMU, aw_bits, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.41.0