Programming Interface Information: This information is NOT intended to be
used as Programming Interfaces of z/VM.

SEG64

Prolog
Control Block Contents
SEG64 DSECT
SEGTB64 DSECT
Storage Layout
Cross Reference
 

SEG64 Control Block Content

SEG64 DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      SEG64          SEGMENT TABLE ENTRY
          00FFFFFF       SEGGPTMH       X'FFFFFFFF' Isolate page-table
                                        origin - High
          00FFF800       SEGGPTML       X'FFFFF800' Isolate page-table
                                        origin - Low
     64-bit mask X'FFFFFFFF80000000'
          00FFFFFF       SEGG2GMH       X'FFFFFFFF' Isolate STE bits
                                        which must be zero in a <2G
                                        ESAME STE - High
          .... ....      SEGG2GML       X'80000000' Isolate STE bits
                                        which must be zero in a <2G
                                        ESAME STE - Low
     64-bit mask X'0000000000000200' 32-bit high X'00000000'
          00000200       SEGGPROM       X'00000200' Isolate segment page
                                        protect bit
     64-bit mask X'0000000000000020' 32-bit high X'00000000'
          ..1. ....      SEGGINVM       X'00000020' Isolate invalid bit
     64-bit mask X'0000000000000010' 32-bit high X'00000000'
          ...1 ....      SEGGCOMM       X'00000010' Isolate
                                        common-segment bit
0000    0 Dbl-Word     8 SEGGENTR       ESAME format segment table entry
          00000008       SEGGLEN        *-SEGGENTR Length of one ESAME
                                        format segment table entry
0008    8 Dbl-Word     8 SEGGNEXT (0)   Next segment table entry
0000    0 Signed       4 SEG64W0        Word 0 of ESAME STE Bits 0-31 of
                                        ESAME PTO
0004    4 Signed       4 SEG64W1        Word 1 of ESAME STE
0004    4 Bitstring    1 * (2)          Bits 32-47 of ESAME PTO
0006    6 Bitstring    1 *              Bits 48-52 of ESAME PTO, plus the
                                        following three bits
          .... ..1.      SEGGPROT       X'02' Entire segment is page
                                        protected
0007    7 Bitstring    1 SEGGSTAT       Segment Table Entry Status
          1... ....      SEGGWAIT       X'80' Segment has translation
                                        requests waiting. SEGINVAL must
                                        be = 1.
          .1.. ....      SEGGTRAN       X'40' Segment is being translated
                                        This bit is used by software to
                                        serialize segment translation.
                                        SEGINVAL must be = 1.
          ..1. ....      SEGGINVL       X'20' Segment Table Entry is
                                        invalid Bits 0-52 of the Segment
                                        Table entry do NOT contain a
                                        valid Page-Table Origin
          ...1 ....      SEGGCOMN       X'10' Common segment bit
          .... 11..      SEGGTTBT       X'0C' Table Type bits - must be
                                        b'00'
          .... ..1.      SEGGXSTR       X'02' Used by CP to indicate that
                                        a PGMBK that resides on XSTORE
                                        supports pages that also reside
                                        on XSTORE.
          .... ...1      SEGGNULL       X'01' Segment cannot be allocated
                                        for guest storage, it is not
                                        addressable by the user. SEGGINVL
                                        must be = 1.
     Note that unlike the ESA/390 segment table entry, the ESAME segment
     table entry contains no page table length information. In ESAME mode,
     all page tables represent a full megabyte of virtual storage (256 page
     table entries).
          00000014       SEGGSHFT       20 Bits to shift by to convert
                                        between segment number and
                                        virtual address.
          00000800       SEGGPTUN       2048 Number of bytes in a
                                        page-table. In ESAME, all page
                                        tables are "full" page tables
                                        containing 256 8 byte entries,
                                        representing 1M of virtual
                                        storage.
          0000000B       SEGGPTUS       11 Number of bits to shift left
                                        in order to multiply by SEGPTUNT.
          00000014       SEGGPXPT       12+8 Bits to shift right an
                                        isolated page index to obtain a
                                        page- table length.
          00000009       SEGGPXDS       12-3 Bits to shift to convert
                                        between an isolated page index
                                        and the displacement into the
                                        page table of the applicable 8
                                        byte ESAME PTE.
          00000008       SEGGPTRM       8 Bits to shift to determine if
                                        an invalid STE contains a PTRM
                                        virtual address.
     FUNCTION : The segment table describes a virtual address space. A
     segment table is made up of contiguous segment table entries. Segment
     tables must begin on 4K page boundaries, and must be of integral
     multiples of the minimum segment table size, 64 bytes for ESA/390 and
     1024 bytes for ESAME.
     For guest primary address spaces of 512MB or less, or for non-primary
     virtual address spaces of 512MB or less, the segment table is allocated
     either as a seperate page of storage or out of the low addresses of a
     GUESTPERM type VMDBK free storage frame.
     For non-guest primary address spaces, such as VM data spaces and system
     address spaces, if the address space is 512MB or smaller, the segment
     table is always allocated either from a seperate page of storage or out
     of the low addresses of a GUESTPERM type VMDBK free storage frame.
     When a virtual address space is defined greater than 512MB in size, up
     to four contiguous pages are allocated.
     The SYSTEM virtual address space is always defined to be 2048MB in size
     and its segment table is always allocated as four contiguous frames of
     storage at system initialization.
     The format of the segment table entry is ARCHITECTED and cannot be
     changed in any way which violates the architecture.
     Located by : ASTSTD field of HCPASTE (ESA/390) ASTASCE field of HCPASTE
     (ESAME) CONTROL REGISTER 1 CONTROL REGISTER 7 PGMSEGTE field of the
     associated PGMBK (if any) VMDPSTD field of HCPVMDBK (ESA/390) VMDPASCE
     field of HCPVMDBK (ESAME) VMDPXSOL field of HCPVMDBK for shadow tables
     Created by : HCPBVMBK when a VMDBK is built HCPFTUSG when an FTC
     address space is built HCPSEGAS when a normal segment table is built
     HCPWLGET when a shadow segment table is built For guest primary address
     space addressability less than or equal to 32 MB, the segment table
     created by HCPBVM (imbedded in the beginning of the VMDBK) which was
     created during LOGON processing is used. HCPBVM always builds this
     segment table regardless of the guest primary virtual address space
     storage size, but it is only used if the actual addressability needed
     is 32MB or less.
     For guest primary address space storage sizes from 33 Megabytes to 1024
     MB, and for all other address spaces less than or equal to 1024 MB, the
     segment table is allocated either as a seperate page or from the low
     addresses of a GUESTPERM type VMDBK free storage page.
     For all address spaces from 1024 MB to 2048 MB in size, two contiguous
     pages are allocated to contain the segment table. If there is enough
     unused storage in the secong page past the end of the segment table,
     the second page may be used for GUESTPERM type VMDBK free storage (with
     the low addresses allocated for use as the segment table).
     Deleted by : HCPSTKFG when a VMDBK is released HCPSEGRS when a normal
     segment table is released HCPWLBRE when a shadow segment table is
     released
     The segment table in guest primary VMDBKs is not deleted until the
     VMDBK itself is deleted (after the guest is logged off). If the guest
     primary virtual storage size at the time of logoff is 32MB or less,
     this is the actual segment table. Normal segment tables allocated
     outside the VMDBK are released whenever the address space is destroyed
     or reset, and may be released when an address space is resized due to
     saved segment imbed/unimbed processing.
     Shadow segment tables are deleted when the owning RGuest base VMDBK is
     destroyed.

SEGTB64 DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      SEGTB64        SEGMENT TABLE
0000    0 Signed       4 SEGGORIG (0)   Segment Table Origin
0000    0 Bitstring    0 * (0)          First STE / SEGTE

 

SEG64 Storage Layout

          
*** SEG64 - SEGMENT TABLE ENTRY
*
*     +-------------------------------------------------------+
*   0 |                       SEGGENTR                        |
*     +-------------------------------------------------------+
*
*** SEG64 - SEGMENT TABLE ENTRY
          
*** Overlay for SEGGENTR in SEG64
*
*     +---------------------------+---------------------------+
*   0 |         SEG64W0           |         SEG64W1           |
*     +---------------------------+---------------------------+
*   8
*
*** Overlay for SEGGENTR in SEG64
          
*** Overlay for SEG64W1 in SEG64
*
*                                 +-------------+------+------+
*   0 ...                       4 |/////////////|//////|:GSTAT|
*                                 +-------------+------+------+
*   8
*
*** Overlay for SEG64W1 in SEG64
          
*** SEGTB64 - SEGMENT TABLE
*
*
*** SEGTB64 - SEGMENT TABLE

 

SEG64 Cross Reference

Symbol         Dspl Value
-------------- ---- -----
SEGGCOMM       0000 10
SEGGCOMN       0007 10
SEGGENTR       0000
SEGGINVL       0007 20
SEGGINVM       0000 20
SEGGLEN        0000 00000008
SEGGNEXT       0008
SEGGNULL       0007 01
SEGGORIG       0000
SEGGPROM       0000 00000200
SEGGPROT       0006 02
SEGGPTMH       0000 00FFFFFF
SEGGPTML       0000 00FFF800
SEGGPTRM       0007 00000008
SEGGPTUN       0007 00000800
SEGGPTUS       0007 0000000B
SEGGPXDS       0007 00000009
SEGGPXPT       0007 00000014
SEGGSHFT       0007 00000014
SEGGSTAT       0007
SEGGTRAN       0007 40
SEGGTTBT       0007 0C
SEGGWAIT       0007 80
SEGGXSTR       0007 02
SEGG2GMH       0000 00FFFFFF
SEGG2GML       0000 00
SEG64W0        0000
SEG64W1        0004

This information is based on z/VM V3R1.0.
Last updated on 29 Mar 2001 at 16:36:06 EDT.
Copyright IBM Corporation, 1990, 2001