[PATCH v2 1/2] qmp: remove virtio_list, search QOM tree instead

[Jonah Palmer <jonah.palmer@oracle.com>]

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 search
the partial paths of '/machine/peripheral/' &
'/machine/peripheral-anon/' in the QOM composition tree for virtio
devices.

A device is found to be a valid virtio device if (1) its canonical path
is of 'TYPE_VIRTIO_DEVICE' and (2) the device has been realized.

[Jonah: In the previous commit I had written that a device is found to
 be a valid virtio device if (1) it has a canonical path ending with
 'virtio-backend'.

 The code now determines if it's a virtio device by appending
 'virtio-backend' (if needed) to a given canonical path and then
 checking that path to see if the device is of type
'TYPE_VIRTIO_DEVICE'.

 The patch also instead now checks to make sure it's a virtio device
 before attempting to check whether the device is realized or not.]

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
---
 hw/virtio/virtio-qmp.c | 128 ++++++++++++++++++++++++++---------------
 hw/virtio/virtio-qmp.h |   8 +--
 hw/virtio/virtio.c     |   6 --
 3 files changed, 82 insertions(+), 60 deletions(-)

diff --git a/hw/virtio/virtio-qmp.c b/hw/virtio/virtio-qmp.c
index b5e1835299..e936cc8ce5 100644
--- a/hw/virtio/virtio-qmp.c
+++ b/hw/virtio/virtio-qmp.c
@@ -668,67 +668,101 @@ VirtioDeviceFeatures *qmp_decode_features(uint16_t device_id, uint64_t bitmap)
 VirtioInfoList *qmp_x_query_virtio(Error **errp)
 {
     VirtioInfoList *list = NULL;
-    VirtioInfo *node;
-    VirtIODevice *vdev;
 
-    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);
+    /* Query the QOM composition tree for virtio devices */
+    qmp_set_virtio_device_list("/machine/peripheral/", &list);
+    qmp_set_virtio_device_list("/machine/peripheral-anon/", &list);
+    if (list == NULL) {
+        error_setg(errp, "No virtio devices found");
+        return NULL;
+    }
+    return list;
+}
+
+/* qmp_set_virtio_device_list:
+ * @ppath: An incomplete peripheral path to search from.
+ * @list: A list of realized virtio devices.
+ * Searches a given incomplete peripheral path (e.g. '/machine/peripheral/'
+ * or '/machine/peripheral-anon/') for realized virtio devices and adds them
+ * to a given list of virtio devices.
+ */
+void qmp_set_virtio_device_list(const char *ppath, VirtioInfoList **list)
+{
+    ObjectPropertyInfoList *plist;
+    VirtioInfoList *node;
+    Error *err = NULL;
+
+    /* Search an incomplete path for virtio devices */
+    plist = qmp_qom_list(ppath, &err);
+    if (err == NULL) {
+        ObjectPropertyInfoList *start = plist;
+        while (plist != NULL) {
+            ObjectPropertyInfo *value = plist->value;
+            GString *path = g_string_new(ppath);
+            g_string_append(path, value->name);
+            g_string_append(path, "/virtio-backend");
+
+            /* Determine if full path is a realized virtio device */
+            VirtIODevice *vdev = qmp_find_virtio_device(path->str);
+            if (vdev != NULL) {
+                node = g_new0(VirtioInfoList, 1);
+                node->value = g_new(VirtioInfo, 1);
+                node->value->path = g_strdup(path->str);
+                node->value->name = g_strdup(vdev->name);
+                QAPI_LIST_PREPEND(*list, node->value);
             }
-           g_string_free(is_realized, true);
+            g_string_free(path, true);
+            plist = plist->next;
         }
-        qobject_unref(obj);
+        qapi_free_ObjectPropertyInfoList(start);
     }
-
-    return list;
 }
 
 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;
+    char *basename;
+
+    /* Append 'virtio-backend' to path if needed */
+    basename = g_path_get_basename(path);
+    if (strcmp(basename, "virtio-backend")) {
+        GString *temp = g_string_new(path);
+        char *last = strrchr(path, '/');
+        if (g_strcmp0(last, "/")) {
+            g_string_append(temp, "/virtio-backend");
+        } else {
+            g_string_append(temp, "virtio-backend");
         }
+        path = g_strdup(temp->str);
+        g_string_free(temp, true);
+    }
 
-        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;
-            }
+    /* Verify the canonical path is a virtio device */
+    Object *obj = object_resolve_path(path, NULL);
+    if (!obj || !object_dynamic_cast(obj, TYPE_VIRTIO_DEVICE)) {
+        object_unref(obj);
+        return NULL;
+    }
+
+    /* Verify the virtio device is realized */
+    QObject *qobj = qmp_qom_get(path, "realized", &err);
+    if (err == NULL) {
+        GString *is_realized = qobject_to_json_pretty(qobj, true);
+        if (!strncmp(is_realized->str, "false", 4)) {
             g_string_free(is_realized, true);
-        } else {
-            /* virtio device doesn't exist in QOM tree */
-            QTAILQ_REMOVE(&virtio_list, vdev, next);
-            qobject_unref(obj);
+            qobject_unref(qobj);
             return NULL;
         }
-        /* device exists in QOM tree & is realized */
-        qobject_unref(obj);
-        return vdev;
+        g_string_free(is_realized, true);
+    } else {
+        qobject_unref(qobj);
+        return NULL;
     }
-    return NULL;
+    qobject_unref(qobj);
+
+    /* Get VirtIODevice object */
+    VirtIODevice *vdev = VIRTIO_DEVICE(obj);
+    return vdev;
 }
 
 VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
diff --git a/hw/virtio/virtio-qmp.h b/hw/virtio/virtio-qmp.h
index 8af5f5e65a..4b2b7875b4 100644
--- a/hw/virtio/virtio-qmp.h
+++ b/hw/virtio/virtio-qmp.h
@@ -15,13 +15,7 @@
 #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;
-
+void qmp_set_virtio_device_list(const char *ppath, VirtioInfoList **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 295a603e58..83c5db3d26 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
  */
@@ -3616,7 +3614,6 @@ 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)
@@ -3631,7 +3628,6 @@ 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;
 }
@@ -3805,8 +3801,6 @@ 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)
-- 
2.39.3