s390x/css: start with cleared cstat/dstat

When executing the start function, we should start with a clear state
regarding subchannel and device status; it is easy to forget updating one
of them after the ccw has been processed.

Note that we don't need to care about resetting the various control
fields: They are cleared by tsch(), and if they were still pending,
we wouldn't be able to execute the start function in the first
place.

Also note that we don't want to clear cstat/dstat if a suspended
subchannel is resumed.

This fixes a bug where we would continue to present channel-program
check in cstat even though later ccw requests for the subchannel
finished without error (i.e. cstat should be 0).

Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
(cherry picked from commit 6b7741c2bedeae2e8c54fffce81723ca0a0c25c0)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 5df450e00bb5b5dacc7260a01f169c08ff316d2d..97d93d56dfce38f407b38fa09bb7f92a8c120afe 100644 (file)
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -392,6 +392,8 @@ static void sch_handle_start_func(SubchDev *sch, ORB *orb)
     path = 0x80;
 
     if (!(s->ctrl & SCSW_ACTL_SUSP)) {
+        s->cstat = 0;
+        s->dstat = 0;
         /* Look at the orb and try to execute the channel program. */
         assert(orb != NULL); /* resume does not pass an orb */
         p->intparm = orb->intparm;