Re: [PATCH v3 27/30] hmp: QAPIfy object_add

[Paolo Bonzini <pbonzini@redhat.com>]

On 15/03/21 12:38, Dr. David Alan Gilbert wrote:
> * Kevin Wolf (kwolf@redhat.com) wrote:
>> Am 15.03.2021 um 10:39 hat Markus Armbruster geschrieben:
>>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>>
>>>> On 13/03/21 14:28, Markus Armbruster wrote:
>>>>> Kevin Wolf <kwolf@redhat.com> writes:
>>>>>
>>>>>> This switches the HMP command object_add from a QemuOpts-based parser to
>>>>>> user_creatable_add_from_str() which uses a keyval parser and enforces
>>>>>> the QAPI schema.
>>>>>>
>>>>>> Apart from being a cleanup, this makes non-scalar properties and help
>>>>>> accessible. In order for help to be printed to the monitor instead of
>>>>>> stdout, the printf() calls in the help functions are changed to
>>>>>> qemu_printf().
>>>>>>
>>>>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>>>>> Acked-by: Peter Krempa <pkrempa@redhat.com>
>>>>>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>>>>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>>>> ---
>>>>>>    monitor/hmp-cmds.c      | 17 ++---------------
>>>>>>    qom/object_interfaces.c | 11 ++++++-----
>>>>>>    hmp-commands.hx         |  2 +-
>>>>>>    3 files changed, 9 insertions(+), 21 deletions(-)
>>>>>>
>>>>>> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
>>>>>> index 3c88a4faef..652cf9ff21 100644
>>>>>> --- a/monitor/hmp-cmds.c
>>>>>> +++ b/monitor/hmp-cmds.c
>>>>>> @@ -1670,24 +1670,11 @@ void hmp_netdev_del(Monitor *mon, const QDict *qdict)
>>>>>>    
>>>>>>    void hmp_object_add(Monitor *mon, const QDict *qdict)
>>>>>>    {
>>>>>> +    const char *options = qdict_get_str(qdict, "object");
>>>>>>        Error *err = NULL;
>>>>>> -    QemuOpts *opts;
>>>>>> -    Object *obj = NULL;
>>>>>> -
>>>>>> -    opts = qemu_opts_from_qdict(qemu_find_opts("object"), qdict, &err);
>>>>>> -    if (err) {
>>>>>> -        goto end;
>>>>>> -    }
>>>>>>    
>>>>>> -    obj = user_creatable_add_opts(opts, &err);
>>>>>> -    qemu_opts_del(opts);
>>>>>> -
>>>>>> -end:
>>>>>> +    user_creatable_add_from_str(options, &err);
>>>>>>        hmp_handle_error(mon, err);
>>>>>> -
>>>>>> -    if (obj) {
>>>>>> -        object_unref(obj);
>>>>>> -    }
>>>>>>    }
>>>>>
>>>>> Doesn't this break the list-valued properties (Memdev member host-nodes,
>>>>> NumaNodeOptions member cpus) exactly the same way that made us keep
>>>>> QemuOpts for qemu-system-FOO -object?
>>>>
>>>> Yes, it does.  I guess it can just be documented, unlike for the command
>>>> line?
>>>
>>> Maybe.  Judgement call, not mine to make.
>>>
>>> Do people create such objects in HMP?  I figure we don't really know.
>>> Educated guess?
>>>
>>> If you try, how does it break?  Is it confusing?  Can you show an
>>> example?
>>
>> (qemu) object_add memory-backend-ram,id=mem,size=4G,policy=bind,host-nodes=0
>> Error: Invalid parameter type for 'host-nodes', expected: array
>> (qemu) object_add memory-backend-ram,id=mem,size=4G,policy=bind,host-nodes.0=0
>> (qemu)
>>
>> HMP is not a stable interface, so changing the syntax didn't feel like a
>> problem to me. I doubt many people do HMP memory hotplug while setting a
>> specific NUMA policy, but it wouldn't change my assessment anyway. I
>> should have made this explicit in the commit message, though.
> 
> I'm OK for it to change, but yes I'd like to have the before/after
> syntax listed somewhere as easy references for people confused.

I think we should try to improve the string-value QObject visitor to 
also allow JSON values in some places, for example to allow

object_add 
memory-backend-ram,id=mem,size=4G,policy=bind,host-nodes=[0,1,2,3]

Paolo