Re: [Qemu-devel] [PATCH v2 2/5] vfio-ccw: concurrent I/O handling

[Cornelia Huck]

On Thu, 24 Jan 2019 11:08:02 +0100
Pierre Morel <address@hidden> wrote:

> On 23/01/2019 11:21, Cornelia Huck wrote:
> > On Tue, 22 Jan 2019 19:33:46 +0100
> > Halil Pasic <address@hidden> wrote:
> >   
> >> On Mon, 21 Jan 2019 12:03:51 +0100
> >> Cornelia Huck <address@hidden> wrote:
> >>  
> >>> --- a/drivers/s390/cio/vfio_ccw_private.h
> >>> +++ b/drivers/s390/cio/vfio_ccw_private.h
> >>> @@ -28,6 +28,7 @@
> >>>    * @mdev: pointer to the mediated device
> >>>    * @nb: notifier for vfio events
> >>>    * @io_region: MMIO region to input/output I/O arguments/results
> >>> + * @io_mutex: protect against concurrent update of I/O structures  
> >>
> >> We could be a bit more specific about what does this mutex guard.
> >> Is it only io_region, or cp, irb and the new regions a well? ->state does
> >> not seem to be covered, but should need some sort of synchronisation
> >> too, or?  
> > 
> > I'm not sure. IIRC Pierre had some ideas about locking in the fsm?
> >   
> 
> Yes I postponed this work to not collide with your patch series.
> 
> Do you think I should provide a new version of the FSM reworking series 
> based on the last comment I got?
> 
> I would take into account that the asynchronous commands will come with 
> your patch series and only provide the framework changes.

This was more an answer to Halil's concerns around state
synchronization. I would prefer to first get this series (or a
variation) into decent shape, and then address state machine handling
on top of that (when we know more about the transitions involved), just
to avoid confusion.

Does that sound reasonable?