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

[Pankaj Gupta]

> 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 */

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com