Re: [PULL 14/15] qdev: Base object creation on QDict rather than QemuOpts

[Markus Armbruster]

Markus Armbruster <armbru@redhat.com> writes:

> Peter Maydell <peter.maydell@linaro.org> writes:
>
>> On Fri, 15 Oct 2021 at 16:01, Kevin Wolf <kwolf@redhat.com> wrote:
>>> QDicts are both what QMP natively uses and what the keyval parser
>>> produces. Going through QemuOpts isn't useful for either one, so switch
>>> the main device creation function to QDicts. By sharing more code with
>>> the -object/object-add code path, we can even reduce the code size a
>>> bit.
>>>
>>> This commit doesn't remove the detour through QemuOpts from any code
>>> path yet, but it allows the following commits to do so.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>> Message-Id: <20211008133442.141332-15-kwolf@redhat.com>
>>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>>> Tested-by: Peter Krempa <pkrempa@redhat.com>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>
>> Hi; we discovered via a report on IRC this this commit broke
>> handling of "array properties", of which one example is:
>> qemu-system-x86_64 -netdev user,id=a -device rocker,len-ports=1,ports[0]=a
>>
>> This used to work, and now fails with
>>  qemu-system-x86_64: -device rocker,len-ports=1,ports[0]=a: Property
>> 'rocker.ports[0]' not found
>>
>> I think this happens because array properties have the
>> requirement that the len-foo property is set first before
>> any of the foo[n] properties can be set. In the old code
>> I guess we used to set properties from the command line
>> in the order they were specified, whereas in the new code
>> we end up in object_set_properties_from_qdict() which
>> tries to set them in whatever order the qdict hash table
>> provides them, which turns out to be the wrong one :-(
>>
>> Any suggestions for how to address this ?
>
> My initial (knee-jerk) reaction to breaking array properties: Faster,
> Pussycat! Kill! Kill!
>
> Back to serious: replace the implementation of QDict so it iterates in
> order?

I just sent

    [RFC PATCH] qobject: Rewrite implementation of QDict for in-order traversal
    Message-Id: <20220705095421.2455041-1-armbru@redhat.com>

Please test whether this fixes the regressions you observed.