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

[Halil Pasic]

On Thu, 24 Jan 2019 11:19:34 +0100
Cornelia Huck <address@hidden> wrote:

> 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?
> 

I would like the two hitting the same kernel release. In that case I'm
fine with deferring some of the concurrency fixes after the csch/hsch
stuff. Otherwise I would have a bad feeling about increasing the
complexity without fixing known bugs.

Regards,
Halil