Re: [Qemu-devel] [PATCH RFC 2/2] qmp: New command qom-new

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/24/2012 08:48 AM, Igor Mammedov wrote:
> On 05/24/2012 03:04 PM, Anthony Liguori wrote:
>> On 05/24/2012 06:43 AM, Markus Armbruster wrote:
>>> To create objects via QMP.
>>>
>>> Test case:
>>>
>>> $ upstream-qemu --enable-kvm -S -m 384 -vnc :0 -monitor stdio -chardev
>>> socket,id=qmp,path=test-qmp,server=on,wait=off -mon mode=control,chardev=qmp
>>>
>>> Conversation on the qmp socket:
>>> {"QMP": {"version": {"qemu": {"micro": 93, "minor": 0, "major": 1},
>>> "package": ""}, "capabilities": []}}
>>> { "execute": "qmp_capabilities" }
>>> {"return": {}}
>>> {"execute":"qom-new","arguments":{"parent":"/xxx",
>>> "prop-name":"test-qmp-new", "type-name":"xxx"}}
>>> {"error": {"class": "DeviceNotFound", "desc": "Device '/xxx' not found",
>>> "data": {"device": "/xxx"}}}
>>> {"execute":"qom-new","arguments":{"parent":"/machine",
>>> "prop-name":"test-qmp-new", "type-name":"xxx"}}
>>> {"error": {"class": "InvalidParameterValue", "desc": "Parameter 'type-name'
>>> expects a type name", "data": {"name": "type-name", "expected": "a type
>>> name"}}}
>>> {"execute":"qom-new","arguments":{"parent":"/machine",
>>> "prop-name":"test-qmp-new", "type-name":"container"}}
>>> {"return": "/machine/test-qmp-new"}
>>> {"execute":"qom-list","arguments":{"path":"/machine"}}
>>> {"return": [{"name": "test-qmp-new", "type": "child<container>"}, {"name":
>>> "i440fx", "type": "child<i440FX-pcihost>"}, {"name": "unattached",
>>> "type": "child<container>"}, {"name": "peripheral", "type":
>>> "child<container>"}, {"name": "peripheral-anon", "type": "child<container>"}]}
>>>
>>> Note: qdev objects (subtype of TYPE_DEVICE) created with qom-new lack
>>> additional magic performed by qdev_try_create(), and almost certainly
>>> won't work.
>>>
>>> Signed-off-by: Markus Armbruster<armbru@redhat.com>
>>> ---
>>> qapi-schema.json | 22 ++++++++++++++++++++++
>>> qmp-commands.hx | 5 +++++
>>> qmp.c | 27 +++++++++++++++++++++++++++
>>> 3 files changed, 54 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/qapi-schema.json b/qapi-schema.json
>>> index 2ca7195..ab9e68b 100644
>>> --- a/qapi-schema.json
>>> +++ b/qapi-schema.json
>>> @@ -1699,6 +1699,28 @@
>>> 'returns': [ 'ObjectTypeInfo' ] }
>>>
>>> ##
>>> +# qom-new:
>>> +#
>>> +# Create a new object
>>> +#
>>> +# @parent: the parent's path within the object model. See @qom-get
>>> +# for a description of paths.
>>> +#
>>> +# @prop-name: the name of the property to add to the parent.
>>> +#
>>> +# @type: the new object's type name
>>> +#
>>> +# Returns: The new object's canonical absolute path
>>> +#
>>> +# Since: 1.2
>>> +#
>>> +# Notes: This command is experimental and may change syntax in future releases.
>>> +##
>>> +{ 'command': 'qom-new',
>>> + 'data': { 'parent': 'str', 'prop-name': 'str', 'type-name': 'str' },
>>> + 'returns': 'str' }
>>> +
>>> +##
>>> # @migrate
>>> #
>>> # Migrates the current running guest to another Virtual Machine.
>>> diff --git a/qmp-commands.hx b/qmp-commands.hx
>>> index db980fa..53adda2 100644
>>> --- a/qmp-commands.hx
>>> +++ b/qmp-commands.hx
>>> @@ -2142,3 +2142,8 @@ EQMP
>>> .args_type = "implements:s?,abstract:b?",
>>> .mhandler.cmd_new = qmp_marshal_input_qom_list_types,
>>> },
>>> + {
>>> + .name = "qom-new",
>>> + .args_type = "parent:s,prop-name:s,type-name:s",
>>> + .mhandler.cmd_new = qmp_marshal_input_qom_new,
>>> + },
>>> diff --git a/qmp.c b/qmp.c
>>> index fee9fb2..cad5610 100644
>>> --- a/qmp.c
>>> +++ b/qmp.c
>>> @@ -417,3 +417,30 @@ ObjectTypeInfoList *qmp_qom_list_types(bool has_implements,
>>>
>>> return ret;
>>> }
>>> +
>>> +char *qmp_qom_new(const char *parent, const char *prop_name,
>>> + const char *type_name, Error **errp)
>>> +{
>>> + Object *p, *obj;
>>> + Type type;
>>> +
>>> + // TODO anything fancy with containger_get() needed?
>>
>> I'm not sure how I feel about this. I never intended for a user to be able to
>> create objects that were arbitrary children of other objects.
>>
>> In some ways, I think this is almost too powerful of an interface to expose to
>> users. I like things like device_add() better that only creates objects
>> of TYPE_DEVICE that are always in /peripherial.
>>
>> For block, we'd have a similar interface that always created objects of
>> TYPE_BLOCK_DRIVER and put them in /block.
>
> Will we have a special cases for every incompatible device types that is going
> to be hot-plugged via device_add monitor command?
>
> For CPUs my thoughts were moving in opposite direction, like:
> - make possible to create and initialize CPU as a regular QOM object

I think we should make CPUs a TYPE_DEVICE.  That hasn't been possible yet but 
with the bus conversion series, it will be.

Regards,

Anthony Liguori