Re: [PULL 04/12] hmp: Simplify qom-set

[David Hildenbrand]

On 03.06.20 13:43, Dr. David Alan Gilbert wrote:
> * David Hildenbrand (david@redhat.com) wrote:
>> On 03.06.20 12:43, Dr. David Alan Gilbert wrote:
>>> * David Hildenbrand (david@redhat.com) wrote:
>>>> On 02.06.20 11:26, Dr. David Alan Gilbert wrote:
>>>>> * Markus Armbruster (armbru@redhat.com) wrote:
>>>>>> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> writes:
>>>>>>
>>>>>>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>>>>>>>
>>>>>>> Simplify qom_set by making it use qmp_qom_set and the JSON parser.
>>>>>>>
>>>>>>> (qemu) qom-get /machine smm
>>>>>>> "auto"
>>>>>>> (qemu) qom-set /machine smm "auto"
>>>>>>>
>>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>>>>> Message-Id: <20200520151108.160598-3-dgilbert@redhat.com>
>>>>>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>>>>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
>>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>>>>>   With 's'->'S' type change suggested by Paolo and Markus
>>>>>>
>>>>>> This is actually more than just simplification, it's disarming a bear
>>>>>> trap: the string visitor is restricted to a subset of the QAPI types,
>>>>>> and when you qom-set a property with a type it can't handle, QEMU
>>>>>> aborts.  I mentioned this in the discussion of possible ways out of the
>>>>>> qom-get impasse, but missed reraising it in patch review.
>>>>>>
>>>>>> A suitably amended commit would be nice, but respinning the PR just for
>>>>>> that may not be worthwhile.
>>>>>
>>>>> A bit late; still as long as we're removing bear traps not adding them.
>>>>
>>>> This breaks qom-set for my (virtio-mem) use case:
>>>>
>>>> echo "qom-set vm0 requested-size 300M" | sudo nc -U /var/tmp/mon_src
>>>> QEMU 5.0.50 monitor - type 'help' for more information
>>>> (qemu) qom-set vm0 requested-size 300M
>>>> Error: Expecting at most one JSON value
>>>
>>> Does qom-set vm0 requested-size 300e6 do the same thing?
>>
>> The property is defined to be of type "size".
>>
>> (qemu) qom-set vm0 requested-size 300e6
>> Error: Parameter 'requested-size' expects uint64
>>
>> (not sure how "size" and "uint64" are mapped here)
> 
> I think the problem here is that the JSON parser is converting anything
> with an 'e' as a float; JSON itself doesn't have the distinction
> between int and float.
> 

(and just to clarify - I assume you are aware - 300e6 != 300M. So the
interface becomes way harder to use in case one wants to specify
properly aligned sizes - 300M vs 314572800)


-- 
Thanks,

David / dhildenb