* Cornelia Huck <cornelia.h...@de.ibm.com> [2017-05-02 18:04:07 +0200]:
> On Tue, 2 May 2017 10:15:19 +0800
> Dong Jia Shi <bjsdj...@linux.vnet.ibm.com> wrote:
>
> > * Auger Eric <eric.au...@redhat.com> [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.
Quotation from PoP:
------------------8<-----------------------------------
Channel-control check is caused by any machine
malfunction affecting channel-subsystem controls.
... ...
Channel-control check may also indicate that an
error has been detected in the information trans-
ferred to or from main storage during an I/O opera-
tion.
... ...
Detection of the channel-control-check condition
causes the current operation, if any, to be terminated
immediately. The subchannel is made status pending
with primary and alert status or with primary, second-
ary, and alert status as a function of the type of termi-
nation, the current subchannel state, and the device
status presented, if any. When the channel sub-
system recognizes a channel-control-check condi-
tion, any previously existing intermediate interruption
condition may or may not be recognized by the chan-
nel subsystem.
------------------>8-----------------------------------
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;
}
--
Dong Jia Shi
