[PATCH v2 10/10] vfio: ccw: Let user wait when busy on IO

Pierre Morel
2018-05-25T10:21:18Z

In the current implementation, we do not want to start a new SSCH
command before the last one ends.

Currently the user needs to poll on the -EBUSY error to
wait before sending a new request.

Let's be friendly with global warming and let the user sleep
until he may send a new request.

Let's make the caller wait until the last SSCH ends.

Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_fsm.c | 4 ++++
drivers/s390/cio/vfio_ccw_ops.c | 6 ++++++
drivers/s390/cio/vfio_ccw_private.h | 1 +
3 files changed, 11 insertions(+)

diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index c37052d..97b74a1 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -200,6 +200,10 @@ static int fsm_irq(struct vfio_ccw_private *private)

if (private->io_trigger)
eventfd_signal(private->io_trigger, 1);
+
+ if (private->io_completion)
+ complete(private->io_completion);
+
return VFIO_CCW_STATE_IDLE;
}

diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index b202e73..39beb6e 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -183,6 +183,7 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
struct vfio_ccw_private *private;
struct ccw_io_region *region;
union scsw *scsw;
+ DECLARE_COMPLETION_ONSTACK(completion);

if (*ppos + count > sizeof(*region))
return -EINVAL;
@@ -196,6 +197,11 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
scsw = (union scsw *) &region->scsw_area;
switch (scsw->cmd.fctl) {
case SCSW_FCTL_START_FUNC:
+ if (private->state == VFIO_CCW_STATE_BUSY) {
+ private->io_completion = &completion;
+ if (wait_for_completion_interruptible(&completion))
+ return -EINTR;
+ }
vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_SSCH_REQ);
break;
default:
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index ab5e37fa..e2e4f6d 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -39,6 +39,7 @@ struct vfio_ccw_private {
struct subchannel *sch;
int state;
struct completion *completion;
+ struct completion *io_completion;
atomic_t avail;
struct mdev_device *mdev;
struct notifier_block nb;
--
2.7.4