[RFC,v4,1/6] qmp: add QMP command x-debug-query-virtio

diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
index 4e4d39a0a48f..0b649f120044 100644
--- a/hw/virtio/Makefile.objs
+++ b/hw/virtio/Makefile.objs
@@ -38,6 +38,8 @@  obj-$(CONFIG_VIRTIO_SERIAL) += virtio-serial-pci.o
 endif
 else
 common-obj-y += vhost-stub.o
+common-obj-y += virtio-stub.o
 endif
 
 common-obj-$(CONFIG_ALL) += vhost-stub.o
+common-obj-$(CONFIG_ALL) += virtio-stub.o
diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
new file mode 100644
index 000000000000..d4a88f5753a9
--- /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_debug_query_virtio(Error **errp)
+{
+    return qmp_virtio_unsupported(errp);
+}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index b6c8ef5bc025..05b640bcc267 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -13,6 +13,8 @@ 
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "qapi/qapi-commands-virtio.h"
+#include "qapi/qapi-visit-virtio.h"
 #include "cpu.h"
 #include "trace.h"
 #include "exec/address-spaces.h"
@@ -28,6 +30,8 @@ 
 #include "sysemu/dma.h"
 #include "sysemu/runstate.h"
 
+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
@@ -3628,6 +3632,7 @@  static void virtio_device_realize(DeviceState *dev, Error **errp)
 
     vdev->listener.commit = virtio_memory_listener_commit;
     memory_listener_register(&vdev->listener, vdev->dma_as);
+    QTAILQ_INSERT_TAIL(&virtio_list, vdev, next);
 }
 
 static void virtio_device_unrealize(DeviceState *dev, Error **errp)
@@ -3646,6 +3651,7 @@  static void virtio_device_unrealize(DeviceState *dev, Error **errp)
         }
     }
 
+    QTAILQ_REMOVE(&virtio_list, vdev, next);
     g_free(vdev->bus_name);
     vdev->bus_name = NULL;
 }
@@ -3802,6 +3808,8 @@  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)
@@ -3812,6 +3820,26 @@  bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)
     return virtio_bus_ioeventfd_enabled(vbus);
 }
 
+VirtioInfoList *qmp_x_debug_query_virtio(Error **errp)
+{
+    VirtioInfoList *list = NULL;
+    VirtioInfoList *node;
+    VirtIODevice *vdev;
+
+    QTAILQ_FOREACH(vdev, &virtio_list, next) {
+        DeviceState *dev = DEVICE(vdev);
+        node = g_new0(VirtioInfoList, 1);
+        node->value = g_new(VirtioInfo, 1);
+        node->value->path = g_strdup(dev->canonical_path);
+        node->value->type = qapi_enum_parse(&VirtioType_lookup, vdev->name,
+                                            VIRTIO_TYPE_UNKNOWN, NULL);
+        node->next = list;
+        list = node;
+    }
+
+    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 b69d51749635..65adce680188 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -111,6 +111,7 @@  struct VirtIODevice
     bool use_guest_notifier_mask;
     AddressSpace *dma_as;
     QLIST_HEAD(, VirtQueue) *vector_queues;
+    QTAILQ_ENTRY(VirtIODevice) next;
 };
 
 typedef struct VirtioDeviceClass {
diff --git a/qapi/Makefile.objs b/qapi/Makefile.objs
index 4673ab7490df..4fae2e37cfc9 100644
--- a/qapi/Makefile.objs
+++ b/qapi/Makefile.objs
@@ -8,7 +8,7 @@  util-obj-y += qapi-util.o
 QAPI_COMMON_MODULES = audio authz block-core block char common control crypto
 QAPI_COMMON_MODULES += dump error introspect job machine migration misc
 QAPI_COMMON_MODULES += net pragma qdev qom rdma rocker run-state sockets tpm
-QAPI_COMMON_MODULES += trace transaction ui
+QAPI_COMMON_MODULES += trace transaction ui virtio
 QAPI_TARGET_MODULES = machine-target misc-target
 QAPI_MODULES = $(QAPI_COMMON_MODULES) $(QAPI_TARGET_MODULES)
 
diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
index 43b0ba0dea22..189f5a0a7383 100644
--- a/qapi/qapi-schema.json
+++ b/qapi/qapi-schema.json
@@ -84,3 +84,4 @@ 
 { 'include': 'misc.json' }
 { 'include': 'misc-target.json' }
 { 'include': 'audio.json' }
+{ 'include': 'virtio.json' }
diff --git a/qapi/virtio.json b/qapi/virtio.json
new file mode 100644
index 000000000000..da59a118dbfb
--- /dev/null
+++ b/qapi/virtio.json
@@ -0,0 +1,68 @@ 
+##
+# = Virtio devices
+##
+
+##
+# @VirtioType:
+#
+# An enumeration of Virtio device types.
+#
+# Since: 5.1.0
+##
+{ 'enum': 'VirtioType',
+  'data': [ 'unknown', 'virtio-9p', 'virtio-blk', 'virtio-serial',
+            'virtio-gpu', 'virtio-input', 'virtio-net', 'virtio-scsi',
+            'vhost-user-fs', 'vhost-vsock', 'virtio-balloon', 'virtio-crypto',
+            'virtio-iommu', 'virtio-pmem', 'virtio-rng' ]
+}
+
+##
+# @VirtioInfo:
+#
+# Information about a given VirtIODevice
+#
+# @path: VirtIO device canonical path.
+#
+# @type: VirtIO device type.
+#
+# Since: 5.1
+#
+##
+{ 'struct': 'VirtioInfo',
+  'data': {
+    'path': 'str',
+    'type': 'VirtioType'
+  }
+}
+
+##
+# @x-debug-query-virtio:
+#
+# Return the list of all VirtIO devices
+#
+# Returns: list of @VirtioInfo
+#
+# Since: 5.1
+#
+# Example:
+#
+# -> { "execute": "x-debug-query-virtio" }
+# <- { "return": [
+#        {
+#            "path": "/machine/peripheral-anon/device[3]/virtio-backend",
+#            "type": "virtio-net"
+#        },
+#        {
+#            "path": "/machine/peripheral-anon/device[1]/virtio-backend",
+#            "type": "virtio-serial"
+#        },
+#        {
+#            "path": "/machine/peripheral-anon/device[0]/virtio-backend",
+#            "type": "virtio-blk"
+#        }
+#      ]
+#    }
+#
+##
+
+{ 'command': 'x-debug-query-virtio', 'returns': ['VirtioInfo'] }
diff --git a/tests/qtest/qmp-cmd-test.c b/tests/qtest/qmp-cmd-test.c
index 9f5228cd9951..a7bf8aab6357 100644
--- a/tests/qtest/qmp-cmd-test.c
+++ b/tests/qtest/qmp-cmd-test.c
@@ -92,6 +92,7 @@  static bool query_is_blacklisted(const char *cmd)
         "query-gic-capabilities", /* arm */
         /* Success depends on target-specific build configuration: */
         "query-pci",              /* CONFIG_PCI */
+        "x-debug-query-virtio",   /* CONFIG_VIRTIO */
         /* Success depends on launching SEV guest */
         "query-sev-launch-measure",
         /* Success depends on Host or Hypervisor SEV support */