VM66320: DYNAMIC MEMORY DOWNGRADE STALL

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Some memory downgrades can stall and never complete
  

Local fix

Problem summary

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  * USERS AFFECTED: All users of z/VM doing memory downgrades    *
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  * PROBLEM DESCRIPTION:                                         *
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  * RECOMMENDATION: APPLY PTF                                    *
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  A memory downgrade can fail to complete (stall).  This occurs
  because guest pages are allowed to be pinned into reconfigurable
  storage, which will block the reconfigurable zone from being
  vacated for the life of the pin.  These offending pins occur
  because the pin notification bits in the Page Status Table Entry
  (PGSTE) were mismanaged, therefore firmware would do the pin
  without notifying CP of it first, thereby failing to give CP a
  chance to move the guest page to someplace that is safe to pin.
  If this does occur, only the memory downgrade stalls.  The
  system itself remains running and responsive.
  

Problem conclusion

• Code in HCPPTA was changed to properly set the pin notification
  bits (PGSPN) in conjunction with pages on the Aging List.  Code
  in HCPALF was changed to properly set the pin notification bits
  when stealing a frame from a User Frame Owned list (UFO) that
  isn't changed and has a copy on auxiliary storage (PAGE
  allocation).  Code in HCPHPC was changed to properly set the
  pin notification bits when setting the logically zero bit
  (PGSZBIT) of a guest page.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UM35783

Modules/Macros

• HCPALF   HCPHPC   HCPPTA
  

Fix information

• Fixed component name

  VM CP CP

• Fixed component ID

  568411202

Applicable component levels

• R720 PSY UM35783

     UP22/01/04 P 2201

Fix is available

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