Re: [Qemu-devel] [PATCH 3/3] qdev: Use qdev_device_add_get_class() for -device <type>, help

["Andreas Färber" <afaerber@suse.de>]

Am 01.11.2014 um 17:45 schrieb Eduardo Habkost:
> On Sat, Nov 01, 2014 at 05:40:20PM +0100, Andreas Färber wrote:
>> Am 01.11.2014 um 16:56 schrieb Eduardo Habkost:
>>> Make sure we try to list properties from classes that can be safely used with
>>> "-device".
>>>
>>> Fixes the following crashes:
>>>
>>>   $ qemu-system-x86_64 -device x86_64-cpu,help
>>>   **
>>>   ERROR:qom/object.c:336:object_initialize_with_type: assertion failed: (type->abstract == false)
>>>   Aborted (core dumped)
>>>   $ qemu-system-x86_64 -device host-x86_64-cpu,help
>>>   qemu-system-x86_64: [...]/target-i386/cpu.c:1329: host_x86_cpu_initfn: Assertion `(kvm_allowed)' failed.
>>>   Aborted (core dumped)
>>>
>>> After applying this patch:
>>>
>>>   $ qemu-system-x86_64 -device x86_64-cpu,help
>>>   Parameter 'driver' expects non-abstract device type
>>>   $ qemu-system-x86_64 -device host-x86_64-cpu,help
>>>   Parameter 'driver' expects pluggable device type
>>>
>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>> ---
>>>  qdev-monitor.c | 9 +++------
>>>  1 file changed, 3 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/qdev-monitor.c b/qdev-monitor.c
>>> index a9702d8..ebfa701 100644
>>> --- a/qdev-monitor.c
>>> +++ b/qdev-monitor.c
>>> @@ -235,12 +235,9 @@ int qdev_device_help(QemuOpts *opts)
>>>          return 0;
>>>      }
>>>  
>>> -    if (!object_class_by_name(driver)) {
>>> -        const char *typename = find_typename_by_alias(driver);
>>> -
>>> -        if (typename) {
>>> -            driver = typename;
>>> -        }
>>> +    qdev_get_device_class(&driver, &local_err);
>>> +    if (local_err) {
>>> +        goto error;
>>>      }
>>>  
>>>      prop_list = qmp_device_list_properties(driver, &local_err);
>>
>> Is dc->cannot_instantiate_with_device_add_yet || (qdev_hotplug &&
>> !dc->hotpluggable) really relevant here? Or should that rather remain
>> outside the common function in 1/3?
> 
> cannot_instantiate_with_device_add_yet makes sure we won't try to
> instantiate classes that are not device_add-safe yet (like X86CPU, that
> has lots of assumptions and side-effects inside instance_init()).

Maybe I'm misunderstanding? Does this code path apply only to device_add
(then you are right) or does it also apply to -device?

Andreas

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