MISSING: Enhanced-DAT Facility 2

[Fish-Git]

Enhanced-DAT Facility 2   (September, 2012)

The enhanced-DAT facility 2 may be available on models implementing z/Architecture. When the facility is installed and enabled, DAT translation may produce either a page-frame real address, a segment-frame absolute address, or a region-frame absolute address, determined by format controls in the region- third-table entry (if any) and the segment-table entry (if any).

Note: The term EDAT-2 applies is used pervasively in this document to describe the condition of when the enhanced-DAT facility 2 is installed in the configuration and enabled by control register 0. See "Enhanced-DAT Terminology:" on page 3-41 for details on this terminology.

When EDAT-2 applies, the following function is available in the DAT process:

• EDAT-1 applies.

• The region-third-table entry includes a RTTE-format control. When the RTTE-format control is zero, DAT proceeds as is the case for when EDAT-1 applies.

• When the RTTE-format control is one, the region-third-table entry also contains the following:
  
  – A region-frame absolute address (rather than a segment-table origin) specifying the absolute storage location of the 2 G-byte block.

  – Access-control bits and a fetch-protection bit which optionally may be used in lieu of the corresponding bits in the region’s individual storage keys

  – A bit which determines the validity of the access-control bits and a fetch-protection bit in the region-third-table entry

The enhanced-DAT facility 2 adds the COMPARE AND REPLACE DAT TABLE entry instruction, providing for the dynamic replacement of valid, attached DAT-table entries, and the selective clearing of any TLB entries created from the replaced entry.

The enhanced-DAT facility 2 also includes enhancements or changes to the following control instructions:

  • INVALIDATE DAT TABLE ENTRY
  • LOAD PAGE-TABLE-ENTRY ADDRESS
  • MOVE PAGE
  • PERFORM FRAME MANAGEMENT FUNCTION
  • TEST PROTECTION

When the enhanced-DAT facility 2 is installed, the enhanced-DAT facility 1 is also installed.

[Fish-Git]

Moved to combined issue #77 "MISSING Facilities support".