[PATCH] vfio-ccw: process ssch with interrupts disabled

[Cornelia Huck <cohuck@redhat.com>]

When we call ssch, an interrupt might already be pending once we
return from the START SUBCHANNEL instruction. Therefore we need to
make sure interrupts are disabled until after we're done with our
processing.

Note that the subchannel lock is the same as the ccwdevice lock that
is mentioned in the documentation for ccw_device_start() and friends.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 drivers/s390/cio/vfio_ccw_fsm.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index ff6963ad6e39..3c800642134e 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -20,12 +20,12 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
 	int ccode;
 	__u8 lpm;
 	unsigned long flags;
+	int ret;
 
 	sch = private->sch;
 
 	spin_lock_irqsave(sch->lock, flags);
 	private->state = VFIO_CCW_STATE_BUSY;
-	spin_unlock_irqrestore(sch->lock, flags);
 
 	orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm);
 
@@ -38,10 +38,12 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
 		 * Initialize device status information
 		 */
 		sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
-		return 0;
+		ret = 0;
+		break;
 	case 1:		/* Status pending */
 	case 2:		/* Busy */
-		return -EBUSY;
+		ret = -EBUSY;
+		break;
 	case 3:		/* Device/path not operational */
 	{
 		lpm = orb->cmd.lpm;
@@ -51,13 +53,16 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
 			sch->lpm = 0;
 
 		if (cio_update_schib(sch))
-			return -ENODEV;
-
-		return sch->lpm ? -EACCES : -ENODEV;
+			ret = -ENODEV;
+		else
+			ret = sch->lpm ? -EACCES : -ENODEV;
+		break;
 	}
 	default:
-		return ccode;
+		ret = ccode;
 	}
+	spin_unlock_irqrestore(sch->lock, flags);
+	return ret;
 }
 
 static void fsm_notoper(struct vfio_ccw_private *private,
-- 
2.14.3