[PATCH v12 3/8] qmp: add QMP command x-query-virtio

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

From: Laurent Vivier <lvivier@redhat.com>

This new command lists all the instances of VirtIODevices with
their canonical QOM path and name.

[Jonah: @virtio_list duplicates information that already exists in
 the QOM composition tree. However, extracting necessary information
 from this tree seems to be a bit convoluted.

 Instead, we still create our own list of realized virtio devices
 but use @qmp_qom_get with the device's canonical QOM path to confirm
 that the device exists and is realized. If the device exists but
 is actually not realized, then we remove it from our list (for
 synchronicity to the QOM composition tree).

 Also, the QMP command @x-query-virtio is redundant as @qom-list
 and @qom-get are sufficient to search '/machine/' for realized
 virtio devices. However, @x-query-virtio is much more convenient
 in listing realized virtio devices.]

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
---
 hw/virtio/meson.build      |  2 ++
 hw/virtio/virtio-stub.c    | 14 ++++++++++
 hw/virtio/virtio.c         | 44 ++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h |  1 +
 qapi/meson.build           |  1 +
 qapi/qapi-schema.json      |  1 +
 qapi/virtio.json           | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qtest/qmp-cmd-test.c |  1 +
 8 files changed, 132 insertions(+)
 create mode 100644 hw/virtio/virtio-stub.c
 create mode 100644 qapi/virtio.json

diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
index 521f7d6..d893f5f 100644
--- a/hw/virtio/meson.build
+++ b/hw/virtio/meson.build
@@ -6,8 +6,10 @@ softmmu_virtio_ss.add(when: 'CONFIG_VHOST', if_false: files('vhost-stub.c'))
 
 softmmu_ss.add_all(when: 'CONFIG_VIRTIO', if_true: softmmu_virtio_ss)
 softmmu_ss.add(when: 'CONFIG_VIRTIO', if_false: files('vhost-stub.c'))
+softmmu_ss.add(when: 'CONFIG_VIRTIO', if_false: files('virtio-stub.c'))
 
 softmmu_ss.add(when: 'CONFIG_ALL', if_true: files('vhost-stub.c'))
+softmmu_ss.add(when: 'CONFIG_ALL', if_true: files('virtio-stub.c'))
 
 virtio_ss = ss.source_set()
 virtio_ss.add(files('virtio.c'))
diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
new file mode 100644
index 0000000..05a81ed
--- /dev/null
+++ b/hw/virtio/virtio-stub.c
@@ -0,0 +1,14 @@
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-virtio.h"
+
+static void *qmp_virtio_unsupported(Error **errp)
+{
+    error_setg(errp, "Virtio is disabled");
+    return NULL;
+}
+
+VirtioInfoList *qmp_x_query_virtio(Error **errp)
+{
+    return qmp_virtio_unsupported(errp);
+}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 7c1b1dd..e59f0d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -13,12 +13,18 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qapi-commands-virtio.h"
+#include "qapi/qapi-commands-qom.h"
+#include "qapi/qapi-visit-virtio.h"
+#include "qapi/qmp/qjson.h"
 #include "cpu.h"
 #include "trace.h"
 #include "qemu/error-report.h"
 #include "qemu/log.h"
 #include "qemu/main-loop.h"
 #include "qemu/module.h"
+#include "qom/object_interfaces.h"
 #include "hw/virtio/virtio.h"
 #include "migration/qemu-file-types.h"
 #include "qemu/atomic.h"
@@ -29,6 +35,9 @@
 #include "sysemu/runstate.h"
 #include "standard-headers/linux/virtio_ids.h"
 
+/* QAPI list of realized VirtIODevices */
+static QTAILQ_HEAD(, VirtIODevice) virtio_list;
+
 /*
  * The alignment to use between consumer and producer parts of vring.
  * x86 pagesize again. This is the default, used by transports like PCI
@@ -3687,6 +3696,7 @@ 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)
@@ -3701,6 +3711,7 @@ 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;
 }
@@ -3874,6 +3885,8 @@ 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)
@@ -3884,6 +3897,37 @@ bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)
     return virtio_bus_ioeventfd_enabled(vbus);
 }
 
+VirtioInfoList *qmp_x_query_virtio(Error **errp)
+{
+    VirtioInfoList *list = NULL;
+    VirtioInfoList *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_new0(VirtioInfoList, 1);
+                node->value = g_new(VirtioInfo, 1);
+                node->value->path = g_strdup(dev->canonical_path);
+                node->value->name = g_strdup(vdev->name);
+                QAPI_LIST_PREPEND(list, node->value);
+            }
+           g_string_free(is_realized, true);
+        }
+        qobject_unref(obj);
+    }
+
+    return list;
+}
+
 static const TypeInfo virtio_device_info = {
     .name = TYPE_VIRTIO_DEVICE,
     .parent = TYPE_DEVICE,
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 90e6080..8f4e4c1 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -110,6 +110,7 @@ struct VirtIODevice
     bool use_guest_notifier_mask;
     AddressSpace *dma_as;
     QLIST_HEAD(, VirtQueue) *vector_queues;
+    QTAILQ_ENTRY(VirtIODevice) next;
 };
 
 struct VirtioDeviceClass {
diff --git a/qapi/meson.build b/qapi/meson.build
index c0c49c1..e332f28 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -48,6 +48,7 @@ qapi_all_modules = [
   'sockets',
   'trace',
   'transaction',
+  'virtio',
   'yank',
 ]
 if have_system
diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
index 4912b97..1512ada 100644
--- a/qapi/qapi-schema.json
+++ b/qapi/qapi-schema.json
@@ -93,3 +93,4 @@
 { 'include': 'audio.json' }
 { 'include': 'acpi.json' }
 { 'include': 'pci.json' }
+{ 'include': 'virtio.json' }
diff --git a/qapi/virtio.json b/qapi/virtio.json
new file mode 100644
index 0000000..aee0e40
--- /dev/null
+++ b/qapi/virtio.json
@@ -0,0 +1,68 @@
+# -*- Mode: Python -*-
+# vim: filetype=python
+#
+
+##
+# = Virtio devices
+##
+
+##
+# @VirtioInfo:
+#
+# Basic information about a given VirtIODevice
+#
+# @path: The VirtIODevice's canonical QOM path
+#
+# @name: Name of the VirtIODevice
+#
+# Since: 7.0
+#
+##
+{ 'struct': 'VirtioInfo',
+  'data': { 'path': 'str',
+            'name': 'str' } }
+
+##
+# @x-query-virtio:
+#
+# Returns a list of all realized VirtIODevices
+#
+# Features:
+# @unstable: This command is meant for debugging.
+#
+# Returns: List of gathered VirtIODevices
+#
+# Since: 7.0
+#
+# Example:
+#
+# -> { "execute": "x-query-virtio" }
+# <- { "return": [
+#        {
+#            "path": "/machine/peripheral-anon/device[4]/virtio-backend",
+#            "name": "virtio-input"
+#        },
+#        {
+#            "path": "/machine/peripheral/crypto0/virtio-backend",
+#            "name": "virtio-crypto"
+#        },
+#        {
+#            "path": "/machine/peripheral-anon/device[2]/virtio-backend",
+#            "name": "virtio-scsi"
+#        },
+#        {
+#            "path": "/machine/peripheral-anon/device[1]/virtio-backend",
+#            "name": "virtio-net"
+#        },
+#        {
+#            "path": "/machine/peripheral-anon/device[0]/virtio-backend",
+#            "name": "virtio-serial"
+#        }
+#      ]
+#    }
+#
+##
+
+{ 'command': 'x-query-virtio',
+  'returns': [ 'VirtioInfo' ],
+  'features': [ 'unstable' ] }
diff --git a/tests/qtest/qmp-cmd-test.c b/tests/qtest/qmp-cmd-test.c
index 7f103ea..fd00ee2 100644
--- a/tests/qtest/qmp-cmd-test.c
+++ b/tests/qtest/qmp-cmd-test.c
@@ -103,6 +103,7 @@ static bool query_is_ignored(const char *cmd)
         "query-gic-capabilities", /* arm */
         /* Success depends on target-specific build configuration: */
         "query-pci",              /* CONFIG_PCI */
+        "x-query-virtio",         /* CONFIG_VIRTIO */
         /* Success depends on launching SEV guest */
         "query-sev-launch-measure",
         /* Success depends on Host or Hypervisor SEV support */
-- 
1.8.3.1