Re: [PATCH v4 2/3] mac_via: fix incorrect creation of mos6522 device in mac_via

[Peter Maydell <peter.maydell@linaro.org>]

On Mon, 9 Mar 2020 at 10:02, Pan Nengyuan <pannengyuan@huawei.com> wrote:
> On 3/9/2020 5:21 PM, Peter Maydell wrote:
> > Could you explain more? My thought is that we should be using
> > sysbus_init_child_obj() and we should be doing it in the init method.
> > Why does that break the tests ? It's the same thing various other
> > devices do.
>
> device-introspect-test do the follow check for each device type:
>
>     qtree_start = qtest_hmp(qts, "info qtree");
>     ...
>     qtest_qmp(qts, "{'execute': 'device-list-properties','arguments': {'typename': %s}}", type);
>     ...
>     qtree_end = qtest_hmp(qts, "info qtree");
>     g_assert_cmpstr(qtree_start, ==, qtree_end);
>
> If we do qdev_set_parent_bus in init, it will check fail when type = 'mac_via'.
> mac_via_init() is called by q800_init(). But it will not be called in qtest(-machine none) in the step qtree_start.
> And after we call 'device-list-properties', mac_via_init() was called and set dev parent bus. We can find these
> devices in the qtree_end. So it break the test on the assert.

Markus, do you know what's happening here? Why is
trying to use sysbus_init_child_obj() breaking the
device-introspect-test for this particular device,
but fine for the other places where we use it?
(Maybe we're accidentally leaking a reference to
something so the sub-device stays on the sysbus
when it should have removed itself when the
device was deinited ?)

> Here is the output:
>
> # Testing device 'mac_via'
>   adb.0=<child<apple-desktop-bus>>
>   drive=<str>            - Node name or ID of a block device to use as a backend
>   irq[0]=<link<irq>>
>   irq[1]=<link<irq>>
>   mac-via[0]=<child<qemu:memory-region>>
>   via1=<child<mos6522-q800-via1>>
>   via1[0]=<child<qemu:memory-region>>
>   via2=<child<mos6522-q800-via2>>
>   via2[0]=<child<qemu:memory-region>>
> qtree_start: bus: main-system-bus
>   type System
>
> qtree_end: bus: main-system-bus
>   type System
>   dev: mos6522-q800-via2, id ""
>     gpio-in "via2-irq" 8
>     gpio-out "sysbus-irq" 1
>     frequency = 0 (0x0)
>     mmio ffffffffffffffff/0000000000000010
>   dev: mos6522-q800-via1, id ""
>     gpio-in "via1-irq" 8
>     gpio-out "sysbus-irq" 1
>     frequency = 0 (0x0)
>     mmio ffffffffffffffff/0000000000000010

thanks
-- PMM