Re: [Qemu-devel] [PATCH 2/2] vl: Partial support for non-scalar properties with -object

[Paolo Bonzini]

On 10/08/2017 14:25, Markus Armbruster wrote:
> We've wanted -object to support non-scalar properties for a while.
> Dan Berrange tried in "[PATCH v4 00/10]Provide a QOM-based
> authorization API".  Review led to the conclusion that we need to
> replace rather than add to QemuOpts.  Initial work towards that goal
> has been merged to provide -blockdev (commit 8746709), but there's
> substantial work left, mostly due to an bewildering array of
> compatibility problems.
> 
> Even if a full solution is still out of reach, we can have a partial
> solution now: accept -object argument in JSON syntax.  This should
> unblock development work that needs non-scalar properties with -object
> 
> The implementation is similar to -blockdev, except we use the new
> infrastructure only for the new JSON case, and stick to QemuOpts for
> the existing KEY=VALUE,... case, to sidestep compatibility problems.
> 
> If we did this for more options, we'd have to factor out common code.
> But for one option, this will do.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  qapi-schema.json | 14 +++++++++++---
>  vl.c             | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 66 insertions(+), 3 deletions(-)
> 
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 802ea53..7ed1db1 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -3618,15 +3618,23 @@
>  { 'command': 'netdev_del', 'data': {'id': 'str'} }
>  
>  ##
> -# @object-add:
> +# @ObjectOptions:
>  #
> -# Create a QOM object.
> +# Options for creating an object.
>  #
>  # @qom-type: the class name for the object to be created
>  #
>  # @id: the name of the new object
>  #
>  # @props: a dictionary of properties to be passed to the backend
> +##
> +{ 'struct': 'ObjectOptions',
> +  'data': {'qom-type': 'str', 'id': 'str', '*props': 'any'} }
> +
> +##
> +# @object-add:
> +#
> +# Create a QOM object.
>  #
>  # Returns: Nothing on success
>  #          Error if @qom-type is not a valid class name
> @@ -3642,7 +3650,7 @@
>  #
>  ##
>  { 'command': 'object-add',
> -  'data': {'qom-type': 'str', 'id': 'str', '*props': 'any'} }
> +  'data': 'ObjectOptions' }
>  
>  ##
>  # @object-del:
> diff --git a/vl.c b/vl.c
> index fd98ed1..db4680b 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2854,8 +2854,32 @@ static bool object_create_delayed(const char *type)
>      return !object_create_initial(type);
>  }
>  
> +typedef struct ObjectOptionsQueueEntry {
> +    ObjectOptions *oo;
> +    Location loc;
> +    QSIMPLEQ_ENTRY(ObjectOptionsQueueEntry) entry;
> +} ObjectOptionsQueueEntry;
> +
> +typedef QSIMPLEQ_HEAD(ObjectOptionsQueue, ObjectOptionsQueueEntry)
> +    ObjectOptionsQueue;
> +
> +ObjectOptionsQueue oo_queue = QSIMPLEQ_HEAD_INITIALIZER(oo_queue);
> +
> +
>  static void object_create(bool (*type_predicate)(const char *))
>  {
> +    ObjectOptionsQueueEntry *e;
> +
> +    QSIMPLEQ_FOREACH(e, &oo_queue, entry) {
> +        if (!type_predicate(e->oo->qom_type)) {
> +            continue;
> +        }
> +        loc_push_restore(&e->loc);
> +        qmp_object_add(e->oo->qom_type, e->oo->id,
> +                       e->oo->has_props, e->oo->props, &error_fatal);
> +        loc_pop(&e->loc);
> +    }
> +
>      if (qemu_opts_foreach(qemu_find_opts("object"),
>                            user_creatable_add_opts_foreach,
>                            type_predicate, NULL)) {
> @@ -4078,6 +4102,29 @@ int main(int argc, char **argv, char **envp)
>  #endif
>                  break;
>              case QEMU_OPTION_object:
> +                /*
> +                 * TODO Use qobject_input_visitor_new_str() instead of
> +                 * QemuOpts, not in addition to.  Not done now because
> +                 * keyval_parse() isn't wart-compatible with QemuOpts.
> +                 */
> +                if (optarg[0] == '{') {
> +                    Visitor *v;
> +                    ObjectOptionsQueueEntry *e;
> +
> +                    v = qobject_input_visitor_new_str(optarg, "qom-type",
> +                                                      &err);
> +                    if (!v) {
> +                        error_report_err(err);
> +                        exit(1);
> +                    }
> +
> +                    e = g_new(ObjectOptionsQueueEntry, 1);
> +                    visit_type_ObjectOptions(v, NULL, &e->oo, &error_fatal);
> +                    visit_free(v);
> +                    loc_save(&e->loc);
> +                    QSIMPLEQ_INSERT_TAIL(&oo_queue, e, entry);
> +                    break;
> +                }
>                  opts = qemu_opts_parse_noisily(qemu_find_opts("object"),
>                                                 optarg, true);
>                  if (!opts) {
> @@ -4525,6 +4572,14 @@ int main(int argc, char **argv, char **envp)
>  
>      object_create(object_create_delayed);
>  
> +    while (!QSIMPLEQ_EMPTY(&oo_queue)) {
> +        ObjectOptionsQueueEntry *e = QSIMPLEQ_FIRST(&oo_queue);
> +
> +        QSIMPLEQ_REMOVE_HEAD(&oo_queue, entry);
> +        qapi_free_ObjectOptions(e->oo);
> +        g_free(e);
> +    }

Why not free the queue entry in object_create, and assert here that it's
empty?

Paolo

> +
>  #ifdef CONFIG_TPM
>      if (tpm_init() < 0) {
>          exit(1);
>