Re: [Qemu-devel] [PATCH v1 1/1] qmp: marking qmp_cpu as deprecated

[Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>]

On 12/18/2017 08:59 AM, Daniel P. Berrange wrote:
> On Mon, Dec 18, 2017 at 08:53:18AM -0200, Daniel Henrique Barboza wrote:
>> qmp_cpu is a nop that was created a while ago in commit 755f196898
>> ("qapi: Convert the cpu command") for the sake of compatibility,
>> due to the existence of hmp_cpu.
>>
>> Today, there is no need or requirement to keep it as is. QMP is
>> meant to be as stateless as possible, thus any QMP command that
>> needs a specific monitor CPU setup should provide it in its
>> arguments, instead of relying in the current QMP monitor state.
>>
>> This patch flags qmp_cpu as deprecated in qemu-doc.texi and changes
>> qmp_cpu body to show a deprecation message if used.
>>
>> Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
>> ---
>> Although I've changed the behavior of qmp_cpu to return an error
>> instead of doing nothing, no errors were found in the Travis
>> build of the patch. Code inspection confirms that qmp_cpu isn't
>> being used in QEMU.
>>
>> A quick inspection in Libvirt code shows that there is no reference
>> to 'qmp_cpu' there either, but to be sure I've CCed Daniel here
>> so he can comment/confirm if Libvirt does not care for this change.
>>
>>   qemu-doc.texi | 6 ++++++
>>   qmp.c         | 2 +-
>>   2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/qemu-doc.texi b/qemu-doc.texi
>> index f7317dfc66..2b63f9a325 100644
>> --- a/qemu-doc.texi
>> +++ b/qemu-doc.texi
>> @@ -2516,6 +2516,12 @@ subsystem image.
>>   The ``convert -s snapshot_id_or_name'' argument is obsoleted
>>   by the ``convert -l snapshot_param'' argument instead.
>>   
>> +@section System emulator machine protocol commands
>> +
>> +@subsection qmp_cpu (since 2.12.0)
>> +
>> +The ``qmp_cpu'' command is deprecated. Do not use this command.
> Just saying it is deprecated doesn't add any useful info, rather
> explain why it is deprecated & what (if anything) to use instead.
> e.g.
>
>    The ``qmp_cpu'' command is a functional no-op. There is no reason
>    to invoke this command and it will be removed with no replacement.

Thanks, I'll add more info in qemu-doc.texi in the next version.

Also, just checked that I didn't touch qapi-schema.json. This is how
it reads about qmp_cpu:


# This command is a nop that is only provided for the purposes of 
compatibility.
#
# Since: 0.14.0
#
# Notes: Do not use this command.

Should we change it to mention that the command is deprecated, something 
like:

# Notes: Do not use this command - it is deprecated and will disappear 
in the future.


Or just adding the deprecation note in qemu-doc.texi is enough?




>
>>   @subsection host_net_add (since 2.10.0)
>> diff --git a/qmp.c b/qmp.c
>> index e8c303116a..d8543d713d 100644
>> --- a/qmp.c
>> +++ b/qmp.c
>> @@ -115,7 +115,7 @@ void qmp_system_powerdown(Error **erp)
>>   
>>   void qmp_cpu(int64_t index, Error **errp)
>>   {
>> -    /* Just do nothing */
>> +    error_setg(errp, "qmp_cpu is deprecated, do not use this command");
>>   }
>>   
>>   void qmp_cpu_add(int64_t id, Error **errp)
> Regards,
> Daniel