[RFC PATCH v5 0/3] vfio-ccw: Fix interrupt handling for HALT/CLEAR

[Eric Farman <farman@linux.ibm.com>]

Hi Conny, Matt, Halil,

Here's the update to my proposed series for handling the collision
between interrupts for START SUBCHANNEL and HALT/CLEAR SUBCHANNEL.
I'm feeling more confident in the state of them now based on the
discussion on v4, so will keep the cover letter brief. :)

I carried patches 1 and 3 from the last version forward, as patch
1 and 2 here. (Thanks, Conny, for the r-b's on them.)

I dropped patches 2 and 4 from the last version, as part of this
newest attempt.  The conversation on patch 4 [1] has formed into
the new patch 3.

As we'd discussed offline last week, I still have the todo for
a more proper audit of the serialization across these codepaths.
But this seems a better, simpler, fix for the code in its current
form, which addresses my problematic test case and does not
impact my usual regression tests. Any further rework for the
serialization [2] will be more invasive, and take a bit longer.

Thanks,
Eric

Changelog:
v4->v5:
 - Applied Conny's r-b to patches 1 and 3
 - Dropped patch 2 and 4
 - Use a "finished" flag in the interrupt completion path

Previous versions:
v4: https://lore.kernel.org/kvm/20210413182410.1396170-1-farman@linux.ibm.com/
v3: https://lore.kernel.org/kvm/20200616195053.99253-1-farman@linux.ibm.com/
v2: https://lore.kernel.org/kvm/20200513142934.28788-1-farman@linux.ibm.com/
v1: https://lore.kernel.org/kvm/20200124145455.51181-1-farman@linux.ibm.com/

References:
[1] https://lore.kernel.org/kvm/2c1c1e73d488673ec39d7c085a343cbd6b50fb41.camel@linux.ibm.com/
[2] https://lore.kernel.org/kvm/20210416164137.23f4631b.cohuck@redhat.com/

Eric Farman (3):
  vfio-ccw: Check initialized flag in cp_init()
  vfio-ccw: Reset FSM state to IDLE inside FSM
  vfio-ccw: Serialize FSM IDLE state with I/O completion

 drivers/s390/cio/vfio_ccw_cp.c  | 4 ++++
 drivers/s390/cio/vfio_ccw_drv.c | 8 +++++---
 drivers/s390/cio/vfio_ccw_fsm.c | 1 +
 drivers/s390/cio/vfio_ccw_ops.c | 2 --
 4 files changed, 10 insertions(+), 5 deletions(-)

-- 
2.25.1