Re: [Qemu-devel] [PATCH v6 10/13] s390x/css: introduce and realize ccw-request callback

[Cornelia Huck]

On Wed, 3 May 2017 10:18:50 +0800
Dong Jia Shi <address@hidden> wrote:

> * Cornelia Huck <address@hidden> [2017-05-02 18:04:07 +0200]:
> 
> > On Tue, 2 May 2017 10:15:19 +0800
> > Dong Jia Shi <address@hidden> wrote:
> > 
> > > * Auger Eric <address@hidden> [2017-05-01 19:28:23 +0200]:
> > 
> > > > >  static void vfio_ccw_io_notifier_handler(void *opaque)
> > > > >  {
> > > > >      VFIOCCWDevice *vcdev = opaque;
> > > > > +    struct ccw_io_region *region = vcdev->io_region;
> > > > > +    S390CCWDevice *cdev = S390_CCW_DEVICE(vcdev);
> > > > > +    CcwDevice *ccw_dev = CCW_DEVICE(cdev);
> > > > > +    SubchDev *sch = ccw_dev->sch;
> > > > > +    SCSW *s = &sch->curr_status.scsw;
> > > > > +    IRB irb;
> > > > >  
> > > > >      if (!event_notifier_test_and_clear(&vcdev->io_notifier)) {
> > > > >          return;
> > > > >      }
> > > > > +
> > > > > +    if (pread(vcdev->vdev.fd, region,
> > > > > +              vcdev->io_region_size, vcdev->io_region_offset) == -1) 
> > > > > {
> > > > is it possible to read less bytes than requested?
> > > Currently, impossible. The kernel side returns either the full region,
> > > or an error.
> > > But we surely could make it more friendly for a partial return. I will
> > > add a check for that case, and generate a channel program check for it.
> > 
> > I think a channel-control check would be more appropriate here.
> 
> Hi Conny,
> 
> After reading PoP 14-43, I think you are right.

(...)

> So I decide to add this piece of code:
> if (size != vcdev->io_region_size) {
>     /* Information transfer error, generate channel-control check. */
>     s->ctrl &= ~SCSW_ACTL_START_PEND;
>     s->cstat = SCSW_CSTAT_CHN_CTRL_CHK;
>     s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
>     s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
>                SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
>     goto read_err;
> }

Looks good.