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vfio-ccw: rework ssch state handling

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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: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Cornelia Huck 2019-01-29 16:13:57 +01:00
parent 71189f263f
commit 690f6a1581
3 changed files with 16 additions and 8 deletions
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19
drivers/s390/cio/vfio_ccw_fsm.c
View File

@ -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,

2
drivers/s390/cio/vfio_ccw_ops.c
View File

@ -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))

3
drivers/s390/cio/vfio_ccw_private.h
View File

@ -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
};