Commit 690f6a15 authored by Cornelia Huck's avatar Cornelia Huck
Browse files

vfio-ccw: rework ssch state handling 



The flow for processing ssch requests can be improved by splitting
the BUSY state:

- CP_PROCESSING: We reject any user space requests while we are in
  the process of translating a channel program and submitting it to
  the hardware. Use -EAGAIN to signal user space that it should
  retry the request.
- CP_PENDING: We have successfully submitted a request with ssch and
  are now expecting an interrupt. As we can't handle more than one
  channel program being processed, reject any further requests with
  -EBUSY. A final interrupt will move us out of this state.
  By making this a separate state, we make it possible to issue a
  halt or a clear while we're still waiting for the final interrupt
  for the ssch (in a follow-on patch).

It also makes a lot of sense not to preemptively filter out writes to
the io_region if we're in an incorrect state: the state machine will
handle this correctly.

Reviewed-by: default avatarEric Farman <farman@linux.ibm.com>
Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
parent 71189f26

drivers/s390/cio/vfio_ccw_fsm.c

+14 −5
Original line number Diff line number Diff line
@@ -28,7 +28,6 @@ static int fsm_io_helper(struct vfio_ccw_private *private) 
	sch = private->sch;



	spin_lock_irqsave(sch->lock, flags);

	private->state = VFIO_CCW_STATE_BUSY;



	orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm);

	if (!orb) {
@@ -46,6 +45,7 @@ static int fsm_io_helper(struct vfio_ccw_private *private) 
		 */

		sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;

		ret = 0;

		private->state = VFIO_CCW_STATE_CP_PENDING;

		break;

	case 1:		/* Status pending */

	case 2:		/* Busy */
@@ -107,6 +107,12 @@ static void fsm_io_busy(struct vfio_ccw_private *private, 
	private->io_region->ret_code = -EBUSY;

}



static void fsm_io_retry(struct vfio_ccw_private *private,

			 enum vfio_ccw_event event)

{

	private->io_region->ret_code = -EAGAIN;

}



static void fsm_disabled_irq(struct vfio_ccw_private *private,

			     enum vfio_ccw_event event)

{
@@ -135,8 +141,7 @@ static void fsm_io_request(struct vfio_ccw_private *private, 
	struct mdev_device *mdev = private->mdev;

	char *errstr = "request";



	private->state = VFIO_CCW_STATE_BUSY;



	private->state = VFIO_CCW_STATE_CP_PROCESSING;

	memcpy(scsw, io_region->scsw_area, sizeof(*scsw));



	if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) {
@@ -181,7 +186,6 @@ static void fsm_io_request(struct vfio_ccw_private *private, 
	}



err_out:

	private->state = VFIO_CCW_STATE_IDLE;

	trace_vfio_ccw_io_fctl(scsw->cmd.fctl, get_schid(private),

			       io_region->ret_code, errstr);

}
@@ -221,7 +225,12 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = { 
		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_request,

		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,

	},

	[VFIO_CCW_STATE_BUSY] = {

	[VFIO_CCW_STATE_CP_PROCESSING] = {

		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,

		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_retry,

		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,

	},

	[VFIO_CCW_STATE_CP_PENDING] = {

		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,

		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,

		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,

drivers/s390/cio/vfio_ccw_ops.c

+0 −2
Original line number Diff line number Diff line
@@ -193,8 +193,6 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev, 
		return -EINVAL;



	private = dev_get_drvdata(mdev_parent_dev(mdev));

	if (private->state != VFIO_CCW_STATE_IDLE)

		return -EACCES;



	region = private->io_region;

	if (copy_from_user((void *)region + *ppos, buf, count))

drivers/s390/cio/vfio_ccw_private.h

+2 −1
Original line number Diff line number Diff line
@@ -63,7 +63,8 @@ enum vfio_ccw_state { 
	VFIO_CCW_STATE_NOT_OPER,

	VFIO_CCW_STATE_STANDBY,

	VFIO_CCW_STATE_IDLE,

	VFIO_CCW_STATE_BUSY,

	VFIO_CCW_STATE_CP_PROCESSING,

	VFIO_CCW_STATE_CP_PENDING,

	/* last element! */

	NR_VFIO_CCW_STATES

};

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