qmp: remove virtio_list, search QOM tree instead

The virtio_list duplicates information about virtio devices that already
exist in the QOM composition tree. Instead of creating this list of
realized virtio devices, search the QOM composition tree instead.

This patch modifies the QMP command qmp_x_query_virtio to instead
recursively search the QOM composition tree for devices of type
'TYPE_VIRTIO_DEVICE'. The device is also checked to ensure it's
realized.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20230926224107.2951144-2-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

3 files changed, 29 insertions, 69 deletions

diff --git a/hw/virtio/virtio-qmp.c b/hw/virtio/virtio-qmp.c
index 7515b09..adebf87 100644
--- a/hw/virtio/virtio-qmp.c
+++ b/hw/virtio/virtio-qmp.c
@@ -667,70 +667,43 @@ VirtioDeviceFeatures *qmp_decode_features(uint16_t device_id, uint64_t bitmap)
     return features;
 }
 
+static int query_dev_child(Object *child, void *opaque)
+{
+    VirtioInfoList **vdevs = opaque;
+    Object *dev = object_dynamic_cast(child, TYPE_VIRTIO_DEVICE);
+    if (dev != NULL && DEVICE(dev)->realized) {
+        VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+        VirtioInfo *info = g_new(VirtioInfo, 1);
+
+        /* Get canonical path & name of device */
+        info->path = object_get_canonical_path(dev);
+        info->name = g_strdup(vdev->name);
+        QAPI_LIST_PREPEND(*vdevs, info);
+    }
+    return 0;
+}
+
 VirtioInfoList *qmp_x_query_virtio(Error **errp)
 {
-    VirtioInfoList *list = NULL;
-    VirtioInfo *node;
-    VirtIODevice *vdev;
+    VirtioInfoList *vdevs = NULL;
 
-    QTAILQ_FOREACH(vdev, &virtio_list, next) {
-        DeviceState *dev = DEVICE(vdev);
-        Error *err = NULL;
-        QObject *obj = qmp_qom_get(dev->canonical_path, "realized", &err);
-
-        if (err == NULL) {
-            GString *is_realized = qobject_to_json_pretty(obj, true);
-            /* virtio device is NOT realized, remove it from list */
-            if (!strncmp(is_realized->str, "false", 4)) {
-                QTAILQ_REMOVE(&virtio_list, vdev, next);
-            } else {
-                node = g_new(VirtioInfo, 1);
-                node->path = g_strdup(dev->canonical_path);
-                node->name = g_strdup(vdev->name);
-                QAPI_LIST_PREPEND(list, node);
-            }
-           g_string_free(is_realized, true);
-        }
-        qobject_unref(obj);
+    /* Query the QOM composition tree recursively for virtio devices */
+    object_child_foreach_recursive(object_get_root(), query_dev_child, &vdevs);
+    if (vdevs == NULL) {
+        error_setg(errp, "No virtio devices found");
     }
-
-    return list;
+    return vdevs;
 }
 
 VirtIODevice *qmp_find_virtio_device(const char *path)
 {
-    VirtIODevice *vdev;
-
-    QTAILQ_FOREACH(vdev, &virtio_list, next) {
-        DeviceState *dev = DEVICE(vdev);
-
-        if (strcmp(dev->canonical_path, path) != 0) {
-            continue;
-        }
-
-        Error *err = NULL;
-        QObject *obj = qmp_qom_get(dev->canonical_path, "realized", &err);
-        if (err == NULL) {
-            GString *is_realized = qobject_to_json_pretty(obj, true);
-            /* virtio device is NOT realized, remove it from list */
-            if (!strncmp(is_realized->str, "false", 4)) {
-                g_string_free(is_realized, true);
-                qobject_unref(obj);
-                QTAILQ_REMOVE(&virtio_list, vdev, next);
-                return NULL;
-            }
-            g_string_free(is_realized, true);
-        } else {
-            /* virtio device doesn't exist in QOM tree */
-            QTAILQ_REMOVE(&virtio_list, vdev, next);
-            qobject_unref(obj);
-            return NULL;
-        }
-        /* device exists in QOM tree & is realized */
-        qobject_unref(obj);
-        return vdev;
+    /* Verify the canonical path is a realized virtio device */
+    Object *dev = object_dynamic_cast(object_resolve_path(path, NULL),
+                                      TYPE_VIRTIO_DEVICE);
+    if (!dev || !DEVICE(dev)->realized) {
+        return NULL;
     }
-    return NULL;
+    return VIRTIO_DEVICE(dev);
 }
 
 VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
@@ -740,7 +713,7 @@ VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
 
     vdev = qmp_find_virtio_device(path);
     if (vdev == NULL) {
-        error_setg(errp, "Path %s is not a VirtIODevice", path);
+        error_setg(errp, "Path %s is not a realized VirtIODevice", path);
         return NULL;
     }
 
diff --git a/hw/virtio/virtio-qmp.h b/hw/virtio/virtio-qmp.h
index 8af5f5e..245a446 100644
--- a/hw/virtio/virtio-qmp.h
+++ b/hw/virtio/virtio-qmp.h
@@ -15,13 +15,6 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/vhost.h"
 
-#include "qemu/queue.h"
-
-typedef QTAILQ_HEAD(QmpVirtIODeviceList, VirtIODevice) QmpVirtIODeviceList;
-
-/* QAPI list of realized VirtIODevices */
-extern QmpVirtIODeviceList virtio_list;
-
 VirtIODevice *qmp_find_virtio_device(const char *path);
 VirtioDeviceStatus *qmp_decode_status(uint8_t bitmap);
 VhostDeviceProtocols *qmp_decode_protocols(uint64_t bitmap);
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d3a22e3..c727e92 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -45,8 +45,6 @@
 #include "standard-headers/linux/virtio_mem.h"
 #include "standard-headers/linux/virtio_vsock.h"
 
-QmpVirtIODeviceList virtio_list;
-
 /*
  * Maximum size of virtio device config space
  */
@@ -3659,7 +3657,6 @@ static void virtio_device_realize(DeviceState *dev, Error **errp)
     vdev->listener.commit = virtio_memory_listener_commit;
     vdev->listener.name = "virtio";
     memory_listener_register(&vdev->listener, vdev->dma_as);
-    QTAILQ_INSERT_TAIL(&virtio_list, vdev, next);
 }
 
 static void virtio_device_unrealize(DeviceState *dev)
@@ -3674,7 +3671,6 @@ static void virtio_device_unrealize(DeviceState *dev)
         vdc->unrealize(dev);
     }
 
-    QTAILQ_REMOVE(&virtio_list, vdev, next);
     g_free(vdev->bus_name);
     vdev->bus_name = NULL;
 }
@@ -3848,8 +3844,6 @@ static void virtio_device_class_init(ObjectClass *klass, void *data)
     vdc->stop_ioeventfd = virtio_device_stop_ioeventfd_impl;
 
     vdc->legacy_features |= VIRTIO_LEGACY_FEATURES;
-
-    QTAILQ_INIT(&virtio_list);
 }
 
 bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)