[PATCH v4 11/11] vfio/ccw: Move FSM open/close to MDEV open/close

Eric Farman
2022-07-07T13:59:06Z

Part of the confusion that has existed is the FSM lifecycle of
subchannels between the common CSS driver and the vfio-ccw driver.
During configuration, the FSM state goes from NOT_OPER to STANDBY
to IDLE, but then back to NOT_OPER. For example:

vfio_ccw_sch_probe: VFIO_CCW_STATE_NOT_OPER
vfio_ccw_sch_probe: VFIO_CCW_STATE_STANDBY
vfio_ccw_mdev_probe: VFIO_CCW_STATE_IDLE
vfio_ccw_mdev_remove: VFIO_CCW_STATE_NOT_OPER
vfio_ccw_sch_remove: VFIO_CCW_STATE_NOT_OPER
vfio_ccw_sch_shutdown: VFIO_CCW_STATE_NOT_OPER

Rearrange the open/close events to align with the mdev open/close,
to better manage the memory and state of the devices as time
progresses. Specifically, make mdev_open() perform the FSM open,
and mdev_close() perform the FSM close instead of reset (which is
both close and open).

This makes the NOT_OPER state a dead-end path, indicating the
device is probably not recoverable without fully probing and
re-configuring the device.

This has the nice side-effect of removing a number of special-cases
where the FSM state is managed outside of the FSM itself (such as
the aforementioned mdev_close() routine).

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_drv.c | 11 +++--------
drivers/s390/cio/vfio_ccw_fsm.c | 34 ++++++++++++++++++++++++---------
drivers/s390/cio/vfio_ccw_ops.c | 26 +++++++++++--------------
3 files changed, 39 insertions(+), 32 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index f98c9915e73d..4804101ccb0f 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -138,7 +138,7 @@ static struct vfio_ccw_private *vfio_ccw_alloc_private(struct subchannel *sch)

private->sch = sch;
mutex_init(&private->io_mutex);
- private->state = VFIO_CCW_STATE_NOT_OPER;
+ private->state = VFIO_CCW_STATE_STANDBY;
INIT_LIST_HEAD(&private->crw);
INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
@@ -222,21 +222,15 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)

dev_set_drvdata(&sch->dev, private);

- vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
- if (private->state == VFIO_CCW_STATE_NOT_OPER)
- goto out_free;
-
ret = mdev_register_device(&sch->dev, &vfio_ccw_mdev_driver);
if (ret)
- goto out_disable;
+ goto out_free;

VFIO_CCW_MSG_EVENT(4, "bound to subchannel %x.%x.%04x\n",
sch->schid.cssid, sch->schid.ssid,
sch->schid.sch_no);
return 0;

-out_disable:
- cio_disable_subchannel(sch);
out_free:
dev_set_drvdata(&sch->dev, NULL);
vfio_ccw_free_private(private);
@@ -264,6 +258,7 @@ static void vfio_ccw_sch_shutdown(struct subchannel *sch)
struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);

vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
+ vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

/**
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index 89eb3feffa41..4b8b623df24f 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -175,6 +175,9 @@ static void fsm_notoper(struct vfio_ccw_private *private,
*/
css_sched_sch_todo(sch, SCH_TODO_UNREG);
private->state = VFIO_CCW_STATE_NOT_OPER;
+
+ /* This is usually handled during CLOSE event */
+ cp_free(&private->cp);
}

/*
@@ -379,9 +382,16 @@ static void fsm_open(struct vfio_ccw_private *private,
spin_lock_irq(sch->lock);
sch->isc = VFIO_CCW_ISC;
ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch);
- if (!ret)
- private->state = VFIO_CCW_STATE_STANDBY;
+ if (ret)
+ goto err_unlock;
+
+ private->state = VFIO_CCW_STATE_IDLE;
spin_unlock_irq(sch->lock);
+ return;
+
+err_unlock:
+ spin_unlock_irq(sch->lock);
+ vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

static void fsm_close(struct vfio_ccw_private *private,
@@ -393,16 +403,22 @@ static void fsm_close(struct vfio_ccw_private *private,
spin_lock_irq(sch->lock);

if (!sch->schib.pmcw.ena)
- goto out_unlock;
+ goto err_unlock;

ret = cio_disable_subchannel(sch);
if (ret == -EBUSY)
vfio_ccw_sch_quiesce(sch);
+ if (ret)
+ goto err_unlock;

-out_unlock:
- private->state = VFIO_CCW_STATE_NOT_OPER;
+ private->state = VFIO_CCW_STATE_STANDBY;
spin_unlock_irq(sch->lock);
cp_free(&private->cp);
+ return;
+
+err_unlock:
+ spin_unlock_irq(sch->lock);
+ vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

/*
@@ -414,16 +430,16 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
[VFIO_CCW_EVENT_IO_REQ] = fsm_io_error,
[VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_error,
[VFIO_CCW_EVENT_INTERRUPT] = fsm_disabled_irq,
- [VFIO_CCW_EVENT_OPEN] = fsm_open,
+ [VFIO_CCW_EVENT_OPEN] = fsm_nop,
[VFIO_CCW_EVENT_CLOSE] = fsm_nop,
},
[VFIO_CCW_STATE_STANDBY] = {
[VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper,
[VFIO_CCW_EVENT_IO_REQ] = fsm_io_error,
[VFIO_CCW_EVENT_ASYNC_REQ] = fsm_async_error,
- [VFIO_CCW_EVENT_INTERRUPT] = fsm_irq,
- [VFIO_CCW_EVENT_OPEN] = fsm_notoper,
- [VFIO_CCW_EVENT_CLOSE] = fsm_close,
+ [VFIO_CCW_EVENT_INTERRUPT] = fsm_disabled_irq,
+ [VFIO_CCW_EVENT_OPEN] = fsm_open,
+ [VFIO_CCW_EVENT_CLOSE] = fsm_notoper,
},
[VFIO_CCW_STATE_IDLE] = {
[VFIO_CCW_EVENT_NOT_OPER] = fsm_notoper,
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 4673b7ddfe20..bc2176421dc5 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -24,17 +24,12 @@ static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
/*
* If the FSM state is seen as Not Operational after closing
* and re-opening the mdev, return an error.
- *
- * Otherwise, change the FSM from STANDBY to IDLE which is
- * normally done by vfio_ccw_mdev_probe() in current lifecycle.
*/
vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
if (private->state == VFIO_CCW_STATE_NOT_OPER)
return -EINVAL;

- private->state = VFIO_CCW_STATE_IDLE;
-
return 0;
}

@@ -121,8 +116,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
vfio_init_group_dev(&private->vdev, &mdev->dev,
&vfio_ccw_dev_ops);

- private->state = VFIO_CCW_STATE_IDLE;
-
VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: create\n",
private->sch->schid.cssid,
private->sch->schid.ssid,
@@ -137,7 +130,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
err_atomic:
vfio_uninit_group_dev(&private->vdev);
atomic_inc(&private->avail);
- private->state = VFIO_CCW_STATE_STANDBY;
return ret;
}

@@ -165,6 +157,10 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
int ret;

+ /* Device cannot simply be opened again from this state */
+ if (private->state == VFIO_CCW_STATE_NOT_OPER)
+ return -EINVAL;
+
private->nb.notifier_call = vfio_ccw_mdev_notifier;

ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY,
@@ -184,6 +180,12 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
if (ret)
goto out_unregister;

+ vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
+ if (private->state == VFIO_CCW_STATE_NOT_OPER) {
+ ret = -EINVAL;
+ goto out_unregister;
+ }
+
return ret;

out_unregister:
@@ -197,13 +199,7 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
struct vfio_ccw_private *private =
container_of(vdev, struct vfio_ccw_private, vdev);

- if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
- (private->state != VFIO_CCW_STATE_STANDBY)) {
- if (!vfio_ccw_mdev_reset(private))
- private->state = VFIO_CCW_STATE_STANDBY;
- /* The state will be NOT_OPER on error. */
- }
-
+ vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
vfio_ccw_unregister_dev_regions(private);
vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
}
--
2.34.1