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

Pierre Morel
2018-04-19T14:48:13Z

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

Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_fsm.c | 3 +++
drivers/s390/cio/vfio_ccw_ops.c | 21 ++++++++++++++++++++-
drivers/s390/cio/vfio_ccw_private.h | 4 +++-
3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index b77b8ad..4140292 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -195,6 +195,9 @@ 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 f0f4071..346532d 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -171,6 +171,8 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
struct vfio_ccw_private *private;
struct ccw_io_region *region;
union scsw *scsw;
+ int max_retries = 5;
+ DECLARE_COMPLETION_ONSTACK(completion);

if (*ppos + count > sizeof(*region))
return -EINVAL;
@@ -185,7 +187,24 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
if ((scsw->cmd.fctl & SCSW_FCTL_START_FUNC) != SCSW_FCTL_START_FUNC)
return -EINVAL;

- vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_SSCH_REQ);
+ do {
+ switch (private->state) {
+ case VFIO_CCW_STATE_BUSY:
+ private->io_completion = &completion;
+ wait_for_completion(&completion);
+ break;
+ case VFIO_CCW_STATE_IDLE:
+ if (!vfio_ccw_fsm_event(private,
+ VFIO_CCW_EVENT_SSCH_REQ))
+ return count;
+ break;
+ default:
+ return -EBUSY;
+ }
+ } while (max_retries--);
+
+ if (max_retries <= 0)
+ return -EBUSY;
if (region->ret_code != 0)
return region->ret_code;

diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index dbef727..7cca078 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;
@@ -93,12 +94,13 @@ enum vfio_ccw_event {
typedef int (fsm_func_t)(struct vfio_ccw_private *);
extern fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS];

-static inline void vfio_ccw_fsm_event(struct vfio_ccw_private *private,
+static inline int vfio_ccw_fsm_event(struct vfio_ccw_private *private,
int event)
{
mutex_lock(&private->state_mutex);
private->state = vfio_ccw_jumptable[private->state][event](private);
mutex_unlock(&private->state_mutex);
+ return private->io_region.ret_code;
}

extern struct workqueue_struct *vfio_ccw_work_q;
--
2.7.4