Re: [PATCH v2 0/9] Move vfio_ccw to the new mdev API

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Sep 13, 2021 at 04:31:54PM -0400, Eric Farman wrote:
> > I rebased it and fixed it up here:
> > 
> > https://github.com/jgunthorpe/linux/tree/vfio_ccw
> > 
> > Can you try again?
> 
> That does address the crash, but then why is it processing a BROKEN
> event? Seems problematic. 

The stuff related to the NOT_OPER looked really wonky to me. I'm
guessing this is the issue - not sure about the pmcw.ena either..

diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index 5ea392959c0711..0d4d4f425befac 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -380,29 +380,19 @@ static void fsm_open(struct vfio_ccw_private *private,
 	spin_unlock_irq(sch->lock);
 }
 
-static void fsm_close(struct vfio_ccw_private *private,
-		      enum vfio_ccw_event event)
+static int flush_sch(struct vfio_ccw_private *private)
 {
 	struct subchannel *sch = private->sch;
 	DECLARE_COMPLETION_ONSTACK(completion);
 	int iretry, ret = 0;
 
-	spin_lock_irq(sch->lock);
-	if (!sch->schib.pmcw.ena)
-		goto err_unlock;
-	ret = cio_disable_subchannel(sch);
-	if (ret != -EBUSY)
-		goto err_unlock;
-
 	iretry = 255;
 	do {
-
 		ret = cio_cancel_halt_clear(sch, &iretry);
-
 		if (ret == -EIO) {
 			pr_err("vfio_ccw: could not quiesce subchannel 0.%x.%04x!\n",
 			       sch->schid.ssid, sch->schid.sch_no);
-			break;
+			return ret;
 		}
 
 		/*
@@ -413,13 +403,28 @@ static void fsm_close(struct vfio_ccw_private *private,
 		spin_unlock_irq(sch->lock);
 
 		if (ret == -EBUSY)
-			wait_for_completion_timeout(&completion, 3*HZ);
+			wait_for_completion_timeout(&completion, 3 * HZ);
 
 		private->completion = NULL;
 		flush_workqueue(vfio_ccw_work_q);
 		spin_lock_irq(sch->lock);
 		ret = cio_disable_subchannel(sch);
 	} while (ret == -EBUSY);
+	return ret;
+}
+
+static void fsm_close(struct vfio_ccw_private *private,
+		      enum vfio_ccw_event event)
+{
+	struct subchannel *sch = private->sch;
+	int ret;
+
+	spin_lock_irq(sch->lock);
+	if (!sch->schib.pmcw.ena)
+		goto err_unlock;
+	ret = cio_disable_subchannel(sch);
+	if (ret == -EBUSY)
+		ret = flush_sch(private);
 	if (ret)
 		goto err_unlock;
 	private->state = VFIO_CCW_STATE_CLOSED;