Re: [PATCH v3 09/11] vfio/ccw: Create a CLOSE FSM event

[Matthew Rosato <mjrosato@xxxxxxxxxxxxx>]

On 6/30/22 4:36 PM, Eric Farman wrote:
> Refactor the vfio_ccw_sch_quiesce() routine to extract the bit that
> disables the subchannel and affects the FSM state. Use this to form
> the basis of a CLOSE event that will mirror the OPEN event, and move
> the subchannel back to NOT_OPER state.
>
> A key difference with that mirroring is that while OPEN handles the
> transition from NOT_OPER => STANDBY, the later probing of the mdev
> handles the transition from STANDBY => IDLE. On the other hand,
> the CLOSE event will move from one of the operating states {IDLE,
> CP_PROCESSING, CP_PENDING} => NOT_OPER. That is, there is no stop
> in a STANDBY state on the deconfigure path.
>
> Add a call to cp_free() in this event, such that it is captured for
> the various permutations of this event.
>
> In the unlikely event that cio_disable_subchannel() returns -EBUSY,
> the remaining logic of vfio_ccw_sch_quiesce() can still be used.
>
> Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>

Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>

> ---
>   drivers/s390/cio/vfio_ccw_drv.c     | 17 +++++------------
>   drivers/s390/cio/vfio_ccw_fsm.c     | 26 ++++++++++++++++++++++++++
>   drivers/s390/cio/vfio_ccw_ops.c     | 14 ++------------
>   drivers/s390/cio/vfio_ccw_private.h |  1 +
>   4 files changed, 34 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> index 7d9189640da3..f98c9915e73d 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -41,13 +41,6 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
>   	DECLARE_COMPLETION_ONSTACK(completion);
>   	int iretry, ret = 0;
>   
> -	spin_lock_irq(sch->lock);
> -	if (!sch->schib.pmcw.ena)
> -		goto out_unlock;
> -	ret = cio_disable_subchannel(sch);
> -	if (ret != -EBUSY)
> -		goto out_unlock;
> -
>   	iretry = 255;
>   	do {
>   
> @@ -74,9 +67,7 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
>   		spin_lock_irq(sch->lock);
>   		ret = cio_disable_subchannel(sch);
>   	} while (ret == -EBUSY);
> -out_unlock:
> -	private->state = VFIO_CCW_STATE_NOT_OPER;
> -	spin_unlock_irq(sch->lock);
> +
>   	return ret;
>   }
>   
> @@ -256,7 +247,7 @@ static void vfio_ccw_sch_remove(struct subchannel *sch)
>   {
>   	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
>   
> -	vfio_ccw_sch_quiesce(sch);
> +	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
>   	mdev_unregister_device(&sch->dev);
>   
>   	dev_set_drvdata(&sch->dev, NULL);
> @@ -270,7 +261,9 @@ static void vfio_ccw_sch_remove(struct subchannel *sch)
>   
>   static void vfio_ccw_sch_shutdown(struct subchannel *sch)
>   {
> -	vfio_ccw_sch_quiesce(sch);
> +	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
> +
> +	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
>   }
>   
>   /**
> diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
> index 2811b2040490..89eb3feffa41 100644
> --- a/drivers/s390/cio/vfio_ccw_fsm.c
> +++ b/drivers/s390/cio/vfio_ccw_fsm.c
> @@ -384,6 +384,27 @@ 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)
> +{
> +	struct subchannel *sch = private->sch;
> +	int ret;
> +
> +	spin_lock_irq(sch->lock);
> +
> +	if (!sch->schib.pmcw.ena)
> +		goto out_unlock;
> +
> +	ret = cio_disable_subchannel(sch);
> +	if (ret == -EBUSY)
> +		vfio_ccw_sch_quiesce(sch);
> +
> +out_unlock:
> +	private->state = VFIO_CCW_STATE_NOT_OPER;
> +	spin_unlock_irq(sch->lock);
> +	cp_free(&private->cp);
> +}
> +
>   /*
>    * Device statemachine
>    */
> @@ -394,6 +415,7 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>   		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_error,
>   		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
>   		[VFIO_CCW_EVENT_OPEN]		= fsm_open,
> +		[VFIO_CCW_EVENT_CLOSE]		= fsm_nop,
>   	},
>   	[VFIO_CCW_STATE_STANDBY] = {
>   		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
> @@ -401,6 +423,7 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>   		[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_STATE_IDLE] = {
>   		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
> @@ -408,6 +431,7 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>   		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_request,
>   		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>   		[VFIO_CCW_EVENT_OPEN]		= fsm_notoper,
> +		[VFIO_CCW_EVENT_CLOSE]		= fsm_close,
>   	},
>   	[VFIO_CCW_STATE_CP_PROCESSING] = {
>   		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
> @@ -415,6 +439,7 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>   		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_retry,
>   		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>   		[VFIO_CCW_EVENT_OPEN]		= fsm_notoper,
> +		[VFIO_CCW_EVENT_CLOSE]		= fsm_close,
>   	},
>   	[VFIO_CCW_STATE_CP_PENDING] = {
>   		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
> @@ -422,5 +447,6 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
>   		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_request,
>   		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
>   		[VFIO_CCW_EVENT_OPEN]		= fsm_notoper,
> +		[VFIO_CCW_EVENT_CLOSE]		= fsm_close,
>   	},
>   };
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
> index a7ea9358e461..fc5b83187bd9 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -33,9 +33,7 @@ static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
>   	 * There are still a lot more instructions need to be handled. We
>   	 * should come back here later.
>   	 */
> -	ret = vfio_ccw_sch_quiesce(sch);
> -	if (ret)
> -		return ret;
> +	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
>   
>   	ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch);
>   	if (!ret)
> @@ -64,7 +62,6 @@ static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
>   		if (vfio_ccw_mdev_reset(private))
>   			return NOTIFY_BAD;
>   
> -		cp_free(&private->cp);
>   		return NOTIFY_OK;
>   	}
>   
> @@ -159,15 +156,9 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
>   
>   	vfio_unregister_group_dev(&private->vdev);
>   
> -	if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
> -	    (private->state != VFIO_CCW_STATE_STANDBY)) {
> -		if (!vfio_ccw_sch_quiesce(private->sch))
> -			private->state = VFIO_CCW_STATE_STANDBY;
> -		/* The state will be NOT_OPER on error. */
> -	}
> +	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
>   
>   	vfio_uninit_group_dev(&private->vdev);
> -	cp_free(&private->cp);
>   	atomic_inc(&private->avail);
>   }
>   
> @@ -217,7 +208,6 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
>   		/* The state will be NOT_OPER on error. */
>   	}
>   
> -	cp_free(&private->cp);
>   	vfio_ccw_unregister_dev_regions(private);
>   	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
>   }
> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
> index 8dff1699a7d9..435d401b8fb9 100644
> --- a/drivers/s390/cio/vfio_ccw_private.h
> +++ b/drivers/s390/cio/vfio_ccw_private.h
> @@ -143,6 +143,7 @@ enum vfio_ccw_event {
>   	VFIO_CCW_EVENT_INTERRUPT,
>   	VFIO_CCW_EVENT_ASYNC_REQ,
>   	VFIO_CCW_EVENT_OPEN,
> +	VFIO_CCW_EVENT_CLOSE,
>   	/* last element! */
>   	NR_VFIO_CCW_EVENTS
>   };