Commit 248b920d authored Sep 08, 2017 by Halil Pasic Committed by Cornelia Huck Sep 19, 2017

s390x/css: drop data-check in interpretation



The architecture says that channel-data check is indicating that
an uncorrected storage (memory) error has been detected in regard
to the data residing in main storage (memory) that is currently
used for an I/O operation. The described detection is done using
the CBC technology.

The ccw interpretation code is however generating a channel-data check
effectively when the (device specific) ccw_cb returns -EFAULT.  In case
of virtio-ccw devices this happens when mapping memory fails, or when a
NULL pointer is encountered. So this behavior is not architecture
conform.

Furthermore the best fit for these situations (null pointer, mapping a
piece of guest memory fails) from architectural perspective the condition
described as the channel subsystem refers to a location that is not
available, which when encountered shall result in a channel-program
check.

To fix this, all we have to do is to get rid of the switch case matching
-EFAULT: the default is generating a channel-program check.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Message-Id: <20170908152446.14606-2-pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

parent 51af0ec9

hw/s390x/css.c

+0 −9

Original line number	Diff line number	Diff line
		@@ -980,15 +980,6 @@ static void sch_handle_start_func_virtual(SubchDev *sch)
		SCSW_STCTL_ALERT \| SCSW_STCTL_STATUS_PEND;
		s->cpa = sch->channel_prog + 8;
		break;
		case -EFAULT:
		/* memory problem, generate channel data check */
		s->ctrl &= ~SCSW_ACTL_START_PEND;
		s->cstat = SCSW_CSTAT_DATA_CHECK;
		s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
		s->ctrl \|= SCSW_STCTL_PRIMARY \| SCSW_STCTL_SECONDARY \|
		SCSW_STCTL_ALERT \| SCSW_STCTL_STATUS_PEND;
		s->cpa = sch->channel_prog + 8;
		break;
		case -EBUSY:
		/* subchannel busy, generate deferred cc 1 */
		s->flags &= ~SCSW_FLAGS_MASK_CC;