Re: [PATCH 01/10] vfio: ccw: Moving state change out of IRQ context

[Pierre Morel]

On 24/04/2018 08:54, Dong Jia Shi wrote:
> * Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> [2018-04-19 16:48:04 +0200]:
>
> [...]
>
> > @@ -94,9 +83,15 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
> >   static void vfio_ccw_sch_irq(struct subchannel *sch)
> >   {
> >   	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
> > +	struct irb *irb = this_cpu_ptr(&cio_irb);
> >
> >   	inc_irq_stat(IRQIO_CIO);
> > -	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
> > +	memcpy(&private->irb, irb, sizeof(*irb));
> > +
> > +	WARN_ON(work_pending(&private->io_work));
> Hmm, why do we need this?

The current design insure that we have not two concurrent SSCH requests.
How ever I want here to track spurious interrupt.
If we implement cancel, halt or clear requests, we also may trigger (AFAIU)
a second interrupts depending on races between instructions, controller 
and device.

We do not need it strongly.

> > +	queue_work(vfio_ccw_work_q, &private->io_work);
> > +	if (private->completion)
> > +		complete(private->completion);
> >   }
> >
> >   static int vfio_ccw_sch_probe(struct subchannel *sch)
> [...]

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