VM66289: PEVM66173 SUBCHANNEL PROTECTION CHECK AFTER CCW TRANSLATION

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Random subchannel protection checks and interface control checks
  (IFCC) are observed when the subchannel key is non-zero on I/O
  to a real DASD issued by z/VM on behalf of a guest.
  Messages similar to the following may be seen on the operator's
  console log:
  
  msHCPERP602I DASD 804C AN INTERFACE CONTROL CHECK OCCURRED
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of z/VM doing I/O with a non-zero  *
  *                 subchannel key                               *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  When a frame is requested to be used for free storage, a frame
  is selected in module HCPALF and examined to determine if the
  frame should be cleared to zeros, and if a SSKE should be done
  to zero out the storage key and fetch protect bit.  This is
  based on the prior usage of the frame.  If the frame was
  previously a user frame (FRMUSER) or non-specific usage (X'00')
  then it is assumed the contents are sensitive and the frame is
  zeroed out.  Additionally, the state of the key is unknown and a
  SSKE is issued to zero out the storage key and fetch protect
  bit.
  
  During frame initialization the frame code of a newly tested
  frame is set to "CP available" (FRMCPAvl) which is an indication
  that the frame was previously a CP frame.  When such a frame is
  selected to be used for free storage, that is, a frame's first
  use is for free storage, this results in the clearing of the
  frame being skipped, and the key and fetch protect bit not being
  zeroed.  If the fetch protect bit had been 1, and the guest
  issues an I/O with a non-zero subchannel key, and a portion of
  this free storage frame is used to hold part of the guest's
  translated CCW, then a protection check will occur.
  

Problem conclusion

• PEVM66173:  Code in HCPISG (frame initialization code) has been
  changed to set a frame code of X'00' when initializing a frame.
  Existing code in HCPALF will detect this frame code, as well as
  FRMUSER, to mean the frame must be cleared, and a SSKE done to
  zero out the storage key and fetch protect bit.
  

Temporary fix

• *********
  * HIPER *
  *********
  FOR RELEASE VM/ESA CP/ESA R720 :
  PREREQ: VM66173
  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:

  UM35556

Modules/Macros

• HCPISG
  

Fix information

• Fixed component name

  VM CP CP

• Fixed component ID

  568411202

Applicable component levels

• R720 PSY UM35561

     UP21/08/06 P 2201 ­

Fix is available

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