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-rw-r--r--hw/virtio/virtio-bus.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 0f69d1c742..d7ec023adf 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -78,17 +78,23 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
         return;
     }
 
-    vdev_has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
-    if (klass->get_dma_as != NULL && has_iommu) {
+    vdev->dma_as = &address_space_memory;
+    if (has_iommu) {
+        vdev_has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
+        /*
+         * Present IOMMU_PLATFORM to the driver iff iommu_plattform=on and
+         * device operational. If the driver does not accept IOMMU_PLATFORM
+         * we fail the device.
+         */
         virtio_add_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM);
-        vdev->dma_as = klass->get_dma_as(qbus->parent);
-        if (!vdev_has_iommu && vdev->dma_as != &address_space_memory) {
-            error_setg(errp,
+        if (klass->get_dma_as) {
+            vdev->dma_as = klass->get_dma_as(qbus->parent);
+            if (!vdev_has_iommu && vdev->dma_as != &address_space_memory) {
+                error_setg(errp,
                        "iommu_platform=true is not supported by the device");
-            return;
+                return;
+            }
         }
-    } else {
-        vdev->dma_as = &address_space_memory;
     }
 }