On 22/09/2017 11:43, Daniel P. Berrange wrote: > On Fri, Sep 22, 2017 at 11:38:31AM +0200, Paolo Bonzini wrote: >> On 22/09/2017 11:36, Daniel P. Berrange wrote: >>> On Fri, Sep 22, 2017 at 05:14:30PM +0800, Peter Xu wrote: >>>> On Fri, Sep 22, 2017 at 10:04:33AM +0100, Daniel P. Berrange wrote: >>>>> On Fri, Sep 22, 2017 at 04:56:10PM +0800, Peter Xu wrote: >>>>>> IOThread is a general framework that contains IO loop environment and a >>>>>> real thread behind. It's also good to be used internally inside qemu. >>>>>> Provide some helpers for it to create iothreads to be used internally. >>>>>> >>>>>> Signed-off-by: Peter Xu <pet...@redhat.com> >>>>>> --- >>>>>> include/sysemu/iothread.h | 8 ++++++++ >>>>>> iothread.c | 21 +++++++++++++++++++++ >>>>>> 2 files changed, 29 insertions(+) >>>>>> >>>>>> diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h >>>>>> index d2985b3..b07663f 100644 >>>>>> --- a/include/sysemu/iothread.h >>>>>> +++ b/include/sysemu/iothread.h >>>>>> @@ -46,4 +46,12 @@ AioContext *iothread_get_aio_context(IOThread >>>>>> *iothread); >>>>>> void iothread_stop_all(void); >>>>>> GMainContext *iothread_get_g_main_context(IOThread *iothread); >>>>>> >>>>>> +/* >>>>>> + * Helpers used to allocate iothreads for internal use. These >>>>>> + * iothreads will not be seen by monitor clients when query using >>>>>> + * "query-iothreads". >>>>>> + */ >>>>>> +IOThread *iothread_create(const char *id, Error **errp); >>>>>> +void iothread_destroy(IOThread *iothread); >>>>>> + >>>>>> #endif /* IOTHREAD_H */ >>>>>> diff --git a/iothread.c b/iothread.c >>>>>> index 44c8944..74e400c 100644 >>>>>> --- a/iothread.c >>>>>> +++ b/iothread.c >>>>>> @@ -354,3 +354,24 @@ GMainContext *iothread_get_g_main_context(IOThread >>>>>> *iothread) >>>>>> >>>>>> return iothread->worker_context; >>>>>> } >>>>>> + >>>>>> +static Object *iothread_get_internal_parent(void) >>>>>> +{ >>>>>> + return container_get(object_get_root(), "/internal-iothreads"); >>>>>> +} >>>>> >>>>> I tend to think we might benefit from having this generalized in the >>>>> QOM API instead. We have object_get_objects_root() for things that >>>>> are created by the mgmt app / user via CLI / QMP. A parallel method >>>>> object_get_internal_root() could be useful for cases like this where >>>>> we want to create user-creatable objects, but not have them be >>>>> visible to the mgmt app / user, as that would confuse the mgmt app. >>>>> >>>>> Example for this scenario - libvirt calls query-iothreads to identify >>>>> IO thread PIDs, and would get very unhappy if the IOThread used by >>>>> the monitor would appear in that response, which is why Peter has >>>>> put it under /internal-iothreads. I think this scenario will apply >>>>> more broadly, so benefit from us having a general helper in QOM. >>>> >>>> Yeah, I can split the patch if we want it to be exposed to public. >>>> >>>> In that case, would the name "object_get_internal_root" be good? >>> >>> Yeah that's fine with me, but lets see if Paolo has any thoughts from >>> the QOM side. >> >> No, I don't. However, I wonder if query-iothreads should have an >> argument to include internal iothreads. > > I guess it depends whether we consider use of iothreads for migration > to be a private impl detail that may be ripped out & replaced at any > time, or a semi-public detail that apps may rely on. Personally I > would suggest it should be a private impl detail of migration code > that is never exposed to anything outside QEMU, so we have flexibility > to change it at will later.
As far as I understood it's not migration, it's the whole monitor that moves to the iothread. So it's a thing that lasts for the whole existence of the QEMU process. But I may be wrong. Paolo Paolo