Re: [Qemu-devel] [RFC PATCH 1/6] utils/python_api: add scripting interface for Qemu with python lib

[Balamuruhan S]

On 8/8/19 6:15 PM, Philippe Mathieu-Daudé wrote:
> On 8/8/19 12:49 PM, Daniel P. Berrangé wrote:
>> On Wed, Aug 07, 2019 at 12:44:40PM +0530, Balamuruhan S wrote:
>>> Adds scripting interface with python library to call functions in
>>> python modules from Qemu that can be used to feed input externally
>>> and without recompiling Qemu that can be used for early development,
>>> testing and can be extended to abstract some of Qemu code out to a
>>> python script to ease maintenance.
>> I admit the use case is interesting, but this is opening a can of
>> worms...
>>
>> Historically the project has held the view that we do not wish
>> to have an mechanism to support loading out of tree code into the
>> QEMU process. Much previously talk was around dlopen'd C plugins,
>> but dynanically loaded Python plugins are doing the same thing
>> at a conceptual level.
>>
>> We didn't wish to expose internals of QEMU in a plugin API to
>> avoid having any kind of API promise across releases.
>>
>> There was also the question of licensing with plugins opening
>> the door for people to extend QEMU with non-free/closed source
>> functionality.
>>
>> While this series only uses the plugin for one fairly obscure
>> device, once a python plugin feature is intergrated in QEMU
>> there will inevitably be requests to use it in further areas
>> of QEMU.
>>
>> IOW, acceptance of this patch is a significant question for
>> the project, and a broader discussion point, than just this
>> PPC feature patch series.
> Since performance is not an issue, we can use a QMP-PyMMIO bridge.
> Most of the functions required are already exposed, Damien completed the
> missing ones in his 'FAULT INJECTION FRAMEWORK' series:
> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg06230.html

will look at this approach and try using QMP-PyMMIO bridge.

Thank you all for review and suggestions.

>
> Maybe we simply need a clearer (better documented) QMP 'MMIO' API?
>