path: root/drivers/s390
diff options
authorEric Farman <>2021-05-11 21:56:31 +0200
committerCornelia Huck <>2021-05-12 12:59:50 +0200
commit2af7a834a435460d546f0cf0a8b8e4d259f1d910 (patch)
tree9805b68f8f006b268524168e7e18eddb03c18f25 /drivers/s390
parent6c02ac4c9211edabe17bda437ac97e578756f31b (diff)
vfio-ccw: Serialize FSM IDLE state with I/O completion
Today, the stacked call to vfio_ccw_sch_io_todo() does three things: 1) Update a solicited IRB with CP information, and release the CP if the interrupt was the end of a START operation. 2) Copy the IRB data into the io_region, under the protection of the io_mutex 3) Reset the vfio-ccw FSM state to IDLE to acknowledge that vfio-ccw can accept more work. The trouble is that step 3 is (A) invoked for both solicited and unsolicited interrupts, and (B) sitting after the mutex for step 2. This second piece becomes a problem if it processes an interrupt for a CLEAR SUBCHANNEL while another thread initiates a START, thus allowing the CP and FSM states to get out of sync. That is: CPU 1 CPU 2 fsm_do_clear() fsm_irq() fsm_io_request() vfio_ccw_sch_io_todo() fsm_io_helper() Since the FSM state and CP should be kept in sync, let's make a note when the CP is released, and rely on that as an indication that the FSM should also be reset at the end of this routine and open up the device for more work. Signed-off-by: Eric Farman <> Acked-by: Matthew Rosato <> Reviewed-by: Cornelia Huck <> Message-Id: <> Signed-off-by: Cornelia Huck <>
Diffstat (limited to 'drivers/s390')
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 8c625b530035..9b61e9b131ad 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -86,6 +86,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
struct vfio_ccw_private *private;
struct irb *irb;
bool is_final;
+ bool cp_is_finished = false;
private = container_of(work, struct vfio_ccw_private, io_work);
irb = &private->irb;
@@ -94,14 +95,21 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
if (scsw_is_solicited(&irb->scsw)) {
cp_update_scsw(&private->cp, &irb->scsw);
- if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING)
+ if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) {
+ cp_is_finished = true;
+ }
memcpy(private->io_region->irb_area, irb, sizeof(*irb));
- if (private->mdev && is_final)
+ /*
+ * Reset to IDLE only if processing of a channel program
+ * has finished. Do not overwrite a possible processing
+ * state if the final interrupt was for HSCH or CSCH.
+ */
+ if (private->mdev && cp_is_finished)
private->state = VFIO_CCW_STATE_IDLE;
if (private->io_trigger)