Rework handling of multiple I/O requests to return -EAGAIN if
we are already processing an I/O request. Introduce a mutex
to disallow concurrent writes to the I/O region.
The expectation is that userspace simply retries the operation
if it gets -EAGAIN.
We currently don't allow multiple ssch requests at the same
time, as we don't have support for keeping channel programs
around for more than one request.
Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
---
drivers/s390/cio/vfio_ccw_drv.c | 1 +
drivers/s390/cio/vfio_ccw_fsm.c | 8 +++-----
drivers/s390/cio/vfio_ccw_ops.c | 31 +++++++++++++++++++----------
drivers/s390/cio/vfio_ccw_private.h | 2 ++
4 files changed, 26 insertions(+), 16 deletions(-)
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index a10cec0e86eb..2ef189fe45ed 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -125,6 +125,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
private->sch = sch;
dev_set_drvdata(&sch->dev, private);
+ mutex_init(&private->io_mutex);
spin_lock_irq(sch->lock);
private->state = VFIO_CCW_STATE_NOT_OPER;
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index cab17865aafe..f6ed934cc565 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -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);
@@ -42,6 +41,8 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
*/
sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
ret = 0;
+ /* Don't allow another ssch for now */
+ private->state = VFIO_CCW_STATE_BUSY;
break;
case 1: /* Status pending */
case 2: /* Busy */
@@ -99,7 +100,7 @@ static void fsm_io_error(struct vfio_ccw_private *private,
static void fsm_io_busy(struct vfio_ccw_private *private,
enum vfio_ccw_event event)
{
- private->io_region->ret_code = -EBUSY;
+ private->io_region->ret_code = -EAGAIN;
}
static void fsm_disabled_irq(struct vfio_ccw_private *private,
@@ -130,8 +131,6 @@ 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;
-
memcpy(scsw, io_region->scsw_area, sizeof(*scsw));
if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) {
@@ -176,7 +175,6 @@ 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);
}
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index f673e106c041..3fa9fc570400 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -169,16 +169,20 @@ static ssize_t vfio_ccw_mdev_read(struct mdev_device *mdev,
{
struct vfio_ccw_private *private;
struct ccw_io_region *region;
+ int ret;
if (*ppos + count > sizeof(*region))
return -EINVAL;
private = dev_get_drvdata(mdev_parent_dev(mdev));
+ mutex_lock(&private->io_mutex);
region = private->io_region;
if (copy_to_user(buf, (void *)region + *ppos, count))
- return -EFAULT;
-
- return count;
+ ret = -EFAULT;
+ else
+ ret = count;
+ mutex_unlock(&private->io_mutex);
+ return ret;
}
static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
@@ -188,25 +192,30 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
{
struct vfio_ccw_private *private;
struct ccw_io_region *region;
+ int ret;
if (*ppos + count > sizeof(*region))
return -EINVAL;
private = dev_get_drvdata(mdev_parent_dev(mdev));
- if (private->state != VFIO_CCW_STATE_IDLE)
+ if (private->state == VFIO_CCW_STATE_NOT_OPER ||
+ private->state == VFIO_CCW_STATE_STANDBY)
return -EACCES;
+ if (!mutex_trylock(&private->io_mutex))
+ return -EAGAIN;
region = private->io_region;
- if (copy_from_user((void *)region + *ppos, buf, count))
- return -EFAULT;
+ if (copy_from_user((void *)region + *ppos, buf, count)) {
+ ret = -EFAULT;
+ goto out_unlock;
+ }
vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_IO_REQ);
- if (region->ret_code != 0) {
- private->state = VFIO_CCW_STATE_IDLE;
- return region->ret_code;
- }
+ ret = (region->ret_code != 0) ? region->ret_code : count;
- return count;
+out_unlock:
+ mutex_unlock(&private->io_mutex);
+ return ret;
}
static int vfio_ccw_mdev_get_device_info(struct vfio_device_info *info)
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 08e9a7dc9176..e88237697f83 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -28,6 +28,7 @@
* @mdev: pointer to the mediated device
* @nb: notifier for vfio events
* @io_region: MMIO region to input/output I/O arguments/results
+ * @io_mutex: protect against concurrent update of I/O structures
* @cp: channel program for the current I/O operation
* @irb: irb info received from interrupt
* @scsw: scsw info
@@ -42,6 +43,7 @@ struct vfio_ccw_private {
struct mdev_device *mdev;
struct notifier_block nb;
struct ccw_io_region *io_region;
+ struct mutex io_mutex;
struct channel_program cp;
struct irb irb;
--
2.17.2
