Re: [PATCH 02/10] vfio: ccw: Transform FSM functions to return state

[Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>]

On 24/04/2018 09:25, Dong Jia Shi wrote:
> * Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> [2018-04-19 16:48:05 +0200]:
>
> > We change the FSM functions to return the next state,
> > and adapt the fsm_func_t function type.
> I think I'd need to read the rest patches to understand why we need this
> one, but no hurt to write some ideas that I noticed at my first glance.
> See below please.
>
> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/s390/cio/vfio_ccw_fsm.c     | 24 ++++++++++++++++--------
> >   drivers/s390/cio/vfio_ccw_private.h |  5 +++--
> >   2 files changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
> > index af88551..2f3108d 100644
> > --- a/drivers/s390/cio/vfio_ccw_fsm.c
> > +++ b/drivers/s390/cio/vfio_ccw_fsm.c
> > @@ -60,7 +60,7 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
> >   	}
> >   }
> >
> > -static void fsm_notoper(struct vfio_ccw_private *private,
> > +static int fsm_notoper(struct vfio_ccw_private *private,
> >   			enum vfio_ccw_event event)
> >   {
> >   	struct subchannel *sch = private->sch;
> > @@ -71,30 +71,34 @@ static void fsm_notoper(struct vfio_ccw_private *private,
> >   	 */
> >   	css_sched_sch_todo(sch, SCH_TODO_UNREG);
> >   	private->state = VFIO_CCW_STATE_NOT_OPER;
> Here..
>
> > +	return private->state;
> >   }
> >
> >   /*
> >    * No operation action.
> >    */
> > -static void fsm_nop(struct vfio_ccw_private *private,
> > +static int fsm_nop(struct vfio_ccw_private *private,
> >   		    enum vfio_ccw_event event)
> >   {
> > +	return private->state;
> >   }
> >
> > -static void fsm_io_error(struct vfio_ccw_private *private,
> > +static int fsm_io_error(struct vfio_ccw_private *private,
> >   			 enum vfio_ccw_event event)
> >   {
> >   	pr_err("vfio-ccw: FSM: I/O request from state:%d\n", private->state);
> >   	private->io_region.ret_code = -EIO;
> > +	return private->state;
> >   }
> >
> > -static void fsm_io_busy(struct vfio_ccw_private *private,
> > +static int fsm_io_busy(struct vfio_ccw_private *private,
> >   			enum vfio_ccw_event event)
> >   {
> >   	private->io_region.ret_code = -EBUSY;
> > +	return private->state;
> >   }
> >
> > -static void fsm_disabled_irq(struct vfio_ccw_private *private,
> > +static int fsm_disabled_irq(struct vfio_ccw_private *private,
> >   			     enum vfio_ccw_event event)
> >   {
> >   	struct subchannel *sch = private->sch;
> > @@ -104,12 +108,13 @@ static void fsm_disabled_irq(struct vfio_ccw_private *private,
> >   	 * successful - should not happen, but we try to disable again.
> >   	 */
> >   	cio_disable_subchannel(sch);
> > +	return private->state;
> >   }
> >
> >   /*
> >    * Deal with the ccw command request from the userspace.
> >    */
> > -static void fsm_io_request(struct vfio_ccw_private *private,
> > +static int fsm_io_request(struct vfio_ccw_private *private,
> >   			   enum vfio_ccw_event event)
> >   {
> >   	union orb *orb;
> > @@ -141,7 +146,7 @@ static void fsm_io_request(struct vfio_ccw_private *private,
> >   			cp_free(&private->cp);
> >   			goto err_out;
> >   		}
> > -		return;
> > +		return private->state;
> >   	} else if (scsw->cmd.fctl & SCSW_FCTL_HALT_FUNC) {
> >   		/* XXX: Handle halt. */
> >   		io_region->ret_code = -EOPNOTSUPP;
> > @@ -154,12 +159,13 @@ static void fsm_io_request(struct vfio_ccw_private *private,
> >
> >   err_out:
> >   	private->state = VFIO_CCW_STATE_IDLE;
> Here..
>
> > +	return private->state;
> >   }
> >
> >   /*
> >    * Got an interrupt for a normal io (state busy).
> >    */
> > -static void fsm_irq(struct vfio_ccw_private *private,
> > +static int fsm_irq(struct vfio_ccw_private *private,
> >   		    enum vfio_ccw_event event)
> >   {
> >   	struct irb *irb = &private->irb;
> > @@ -172,6 +178,8 @@ static void fsm_irq(struct vfio_ccw_private *private,
> >
> >   	if (private->io_trigger)
> >   		eventfd_signal(private->io_trigger, 1);
> > +
> > +	return private->state;
> >   }
> >
> >   /*
> > diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
> > index 78a66d9..f526b18 100644
> > --- a/drivers/s390/cio/vfio_ccw_private.h
> > +++ b/drivers/s390/cio/vfio_ccw_private.h
> > @@ -83,13 +83,14 @@ enum vfio_ccw_event {
> >   /*
> >    * Action called through jumptable.
> >    */
> > -typedef void (fsm_func_t)(struct vfio_ccw_private *, enum vfio_ccw_event);
> > +typedef int (fsm_func_t)(struct vfio_ccw_private *, enum vfio_ccw_event);
> >   extern fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS];
> >
> >   static inline void vfio_ccw_fsm_event(struct vfio_ccw_private *private,
> >   				     int event)
> >   {
> > -	vfio_ccw_jumptable[private->state][event](private, event);
> > +	private->state = vfio_ccw_jumptable[private->state][event](private,
> > +								   event);
> Since here it assigns new value to private->state, there is no need to
> do that inside each fsm_func?
Absolutely.
I just kept the previous code, just adding the return private->state in 
the functions
in this patch.
merging the state and the return value is done in a later patch.
If you prefer I can do it in this patch.

> >   }
> >
> >   extern struct workqueue_struct *vfio_ccw_work_q;
> > --
> > 2.7.4

--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany