** Changed in: ubuntu-z-systems
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1805414

Title:
  [Ubuntu] kernel: zcrypt: reinit ap queue state machine

Status in Ubuntu on IBM z Systems:
  Fix Released
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Fix Released
Status in linux source package in Disco:
  Fix Released

Bug description:
  == SRU Justification ==
  The vfio device driver when receiving an ap queue device does
                additional resets thereby removing the registration for
                interrupts for the ap device done by the ap bus core
                code. So when later the vfio driver releases the device and
                one of the default zcrypt drivers takes care of the device
                the interrupt registration needs to get renewed. The current
                code does no renew and result is that requests send into such
                a queue will never see a reply processed - the application
                hangs.

  This commit has also been cc'd to upstream stable.

  == Fix ==
  104f708fd ("s390/zcrypt: reinit ap queue state machine during device probe")

  == Regression Potential ==
  Low.  Limited to s390.

  
  == Original Bug Description ==
  Description:  kernel: zcrypt: reinit ap queue state machine

  Symptom:      Zcrypt ap queue device not operational at host level after a
                kvm guest used it.

  Problem:      The vfio device driver when receiving an ap queue device does
                additional resets thereby removing the registration for
                interrupts for  the ap device done by the ap bus core
                code. So when later the vfio driver releases the device and
                one of the default zcrypt drivers takes care of the device
                the interrupt registration needs to get renewed. The current
                code does no renew and result is that requests send into such
                a queue will never see a reply processed - the application
                hangs.

  Solution:     This patch adds a function which resets the aq queue state
                machine for the ap queue device and triggers the walk through
                the initial states (which are reset and registration for
                interrupts). This function is now called before the driver's
                probe function is invoked.
                When the association between driver and device is released,
                the driver's remove function is called. The current
                implementation calls a ap queue function
                ap_queue_remove(). This invokation has been moved to the ap
                bus function to make the probe / remove pair for ap bus and
                drivers more symmetric.

  Reproduction: Set up an kvm guest to use one or more ap queues in
                pass-through mode. Start the guest. Stop the guest. Reassign
                the ap resources back to the host system. Run an application
                which uses exactly this ap resources. Without the fix, the
                application hangs; with the fix the application should run
                fine.

  Upstream commit(s):
  104f708fd1241b22f808bdf066ab67dc5a051de5
  Available on kernel.org

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