qmp: add QMP command x-query-virtio-status

This new command shows the status of a VirtIODevice, including
its corresponding vhost device's status (if active).

Next patch will improve output by decoding feature bits, including
vhost device's feature bits (backend, protocol, acked, and features).
Also will decode status bits of a VirtIODevice.

[Jonah: From patch v12; added a check to @virtio_device_find to ensure
 synchronicity between @virtio_list and the devices in the QOM
 composition tree.]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-3-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 109 insertions, 0 deletions

diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
index 05a81edc92..0b432e8de7 100644
--- a/hw/virtio/virtio-stub.c
+++ b/hw/virtio/virtio-stub.c
@@ -12,3 +12,8 @@ VirtioInfoList *qmp_x_query_virtio(Error **errp)
 {
     return qmp_virtio_unsupported(errp);
 }
+
+VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
+{
+    return qmp_virtio_unsupported(errp);
+}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4fc7c80d3f..696e19126a 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3948,6 +3948,110 @@ VirtioInfoList *qmp_x_query_virtio(Error **errp)
     return list;
 }
 
+static VirtIODevice *virtio_device_find(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;
+    }
+    return NULL;
+}
+
+VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
+{
+    VirtIODevice *vdev;
+    VirtioStatus *status;
+
+    vdev = virtio_device_find(path);
+    if (vdev == NULL) {
+        error_setg(errp, "Path %s is not a VirtIODevice", path);
+        return NULL;
+    }
+
+    status = g_new0(VirtioStatus, 1);
+    status->name = g_strdup(vdev->name);
+    status->device_id = vdev->device_id;
+    status->vhost_started = vdev->vhost_started;
+    status->guest_features = vdev->guest_features;
+    status->host_features = vdev->host_features;
+    status->backend_features = vdev->backend_features;
+
+    switch (vdev->device_endian) {
+    case VIRTIO_DEVICE_ENDIAN_LITTLE:
+        status->device_endian = g_strdup("little");
+        break;
+    case VIRTIO_DEVICE_ENDIAN_BIG:
+        status->device_endian = g_strdup("big");
+        break;
+    default:
+        status->device_endian = g_strdup("unknown");
+        break;
+    }
+
+    status->num_vqs = virtio_get_num_queues(vdev);
+    status->status = vdev->status;
+    status->isr = vdev->isr;
+    status->queue_sel = vdev->queue_sel;
+    status->vm_running = vdev->vm_running;
+    status->broken = vdev->broken;
+    status->disabled = vdev->disabled;
+    status->use_started = vdev->use_started;
+    status->started = vdev->started;
+    status->start_on_kick = vdev->start_on_kick;
+    status->disable_legacy_check = vdev->disable_legacy_check;
+    status->bus_name = g_strdup(vdev->bus_name);
+    status->use_guest_notifier_mask = vdev->use_guest_notifier_mask;
+    status->has_vhost_dev = vdev->vhost_started;
+
+    if (vdev->vhost_started) {
+        VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+        struct vhost_dev *hdev = vdc->get_vhost(vdev);
+
+        status->vhost_dev = g_new0(VhostStatus, 1);
+        status->vhost_dev->n_mem_sections = hdev->n_mem_sections;
+        status->vhost_dev->n_tmp_sections = hdev->n_tmp_sections;
+        status->vhost_dev->nvqs = hdev->nvqs;
+        status->vhost_dev->vq_index = hdev->vq_index;
+        status->vhost_dev->features = hdev->features;
+        status->vhost_dev->acked_features = hdev->acked_features;
+        status->vhost_dev->backend_features = hdev->backend_features;
+        status->vhost_dev->protocol_features = hdev->protocol_features;
+        status->vhost_dev->max_queues = hdev->max_queues;
+        status->vhost_dev->backend_cap = hdev->backend_cap;
+        status->vhost_dev->log_enabled = hdev->log_enabled;
+        status->vhost_dev->log_size = hdev->log_size;
+    }
+
+    return status;
+}
+
 static const TypeInfo virtio_device_info = {
     .name = TYPE_VIRTIO_DEVICE,
     .parent = TYPE_DEVICE,