VM65933: CMS GUEST CAN HAVE PAGE ZEROED IF USING DIAG X'214'

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• If a guest uses any of the CANCEL Pending Page Release
  functionality, diagnose x'214' subcode x'01, x'02', or x'03'
  a page of data could unexpectedly be reverted to zeros.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users using DIAGNOSE X'214'              *
  *                 subcodes x'01', x'02, or x'03'               *
  *                 Cancel Pending Page Release, CPR,            *
  *                 Cancel All Pending Releases, CAPR,           *
  *                 Cancel Pending Release and Validate,         *
  *                 CPRV.                                        *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  Guests that use any form of Pending Page Release Cancel
  function, Diagnose x'214' subcode x'01', x'02, or x'03' can
  randomly have a page of storage zeroed.  This can lead to guest
  ABENDS and incorrect processing.
  

Problem conclusion

• Pending Page Release uses a buffer to hold the address of the
  guest pages pending release.  Pointers are used to manipulate
  the contents of the buffer and point to the next available
  slot to put a pending page to be released in. The list is
  maintained in order from low storage to high storage.
  
  It is possible for a guest to Cancel a Pending Page Release.  A
  Cancel Pending Page Release manipulates the pointer and contents
  of the buffer so that either a page or range of pages are not
  removed from guest storage.  When CP decides to purge the table
  all entries in the table are purged. In this particular case
  there was one page in the Pending Purge Buffer, followed by
  cancel Pending Page Release, the pointers were adjusted to point
  to the begininning of the buffer, but the entry remained.  When
  Purge was initiated the contents of the buffer was purged.
  
  Purging the contents caused the next reference of the page to be
  reinstantiated.  HCPPPR was updated to determine if it was
  already pointing to the beginning of the buffer prior to purging
  the contents, therefore preventing the page from being zeroed.
  

Temporary fix

• *********
  * HIPER *
  *********
  FOR RELEASE VM/ESA CP/ESA R640 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  FOR RELEASE VM/ESACP/ESAR710 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

APAR Information

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

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

  UM35488 UM35494

Modules/Macros

• HCPPPR
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R640 PSY UM35488

     UP20/01/29 P 2001 ¢

• R710 PSY UM35494

     UP20/01/29 P 2101 ¢

Fix is available

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