Re: [Qemu-devel] [PATCH v9 05/10] move out net queue structs define

[Daniel P. Berrange]

On Mon, Sep 07, 2015 at 07:41:26PM +0800, Yang Hongyang wrote:
> 
> 
> On 09/07/2015 07:00 PM, Daniel P. Berrange wrote:
> >On Mon, Sep 07, 2015 at 06:53:49PM +0800, Yang Hongyang wrote:
> >>On 09/07/2015 05:11 PM, Stefan Hajnoczi wrote:
> >>[...]
> >>>>Thanks very much for the suggestion, I've already implemented it and 
> >>>>tested,
> >>>>the code looks cleaner now.
> >>>>
> >>>>The last issue is the QOM thing, do Markus and Andreas have more input
> >>>>about that?
> >>>
> >>>If you would like to see examples of QOM usage, take a look at
> >>>iothread.c and/or backends/hostmem.c.
> >>>
> >>>The key things are:
> >>>
> >>>1. They use include/qom/object.h to register a type based on
> >>>    TYPE_OBJECT and their properties are registered using
> >>>    object_property_add_*().
> >>>
> >>>2. They implement the TYPE_USER_CREATABLE interface so the -object
> >>>    command-line option can be used to instantiate them.  See
> >>>    object_interfaces.h.
> >>>
> >>>As a result, a lot of code becomes unnecessary and iothread.c, in
> >>>particular, is quite short.
> >>
> >>After looking into this, I have some questions on the implement, could you
> >>please help me on this because I don't know much about the object mechanism:
> >>
> >>The netfilter need to be initialized after the net_init_clients, because we
> >>need to attach the filter to the net client. But currently, net client is 
> >>not
> >>using QOM, and seems that it is initialized after objects been created. So 
> >>here
> >>comes the problem: how can I initialize a certain object later, is it 
> >>possiable?
> >
> >It is currently a bit hacky - most objects are initialized very early,
> >but we have a similar problem with rng-egd which must be created /after/
> >chardevs. To deal with this in vl.c main() we have two helper methods
> >object_create_initial and object_create_delayed. The delayed method though
> >still happens before the net clients are created. We could probably just
> >move the objec_create_delayed method invokation to later on, after net
> >clients are created, but if that doesn't work just add an extra helper
> >object_create_very_delayed :-)
> 
> If it's ok to move creation of "rng-egd" later, then "move the
> objec_create_delayed method invokation after net clients are created" should
> solve the problem.

I think it should be ok, because IIRC, the only requirement from rng-egd
was that it be created /after/ -device is processed, so moving it even
later shouldn't hurt it

Regards,
Daniel
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