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

#### SEGTE

Prolog

Control Block Contents
SEGTE DSECT
SEGTB DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### SEGTE Prolog

     NAME       : HCPSEGTE
     DESCRIPTION: SEGMENT TABLE ENTRY
     DSECT      : SEGTE
     Function   : There is one segment table entry for each
                  megabyte of address space.  A segment table is
                  made up of contiguous segment table entries.
                  For details on the segment table, see the SEGTB
                  DSECT definition below.
                  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
                  CONTROL REGISTER 1
                  CONTROL REGISTER 7
                  PGMSEGTE  field of the associated PGMBK (if any)
                  STLSTEPT  field of HCPSTLBK
                  STLSTE2   field of HCPSTLBK
                  VMDPSTD   field of HCPVMDBK
                  VMDPXSOL  field of HCPVMDBK for shadow tables
                  Note that STEs pointed to from the STLBK fields
                  STLSTEPT and STLSTE2 are only "templates" used
                  during saved segment processing, and are never
                  *attached* (accessible by DAT hardware) in the
                  architectural sense.
     Created by : HCPBPBSL  when an STLBK is built
                  HCPBPCBS  when an STLBK is built
                  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
                  and their clones
     Deleted by : HCPBPCBS  when an STLBK is released
                  HCPRPSSL  when an STLBK is released
                  HCPSTKFG  when a VMDBK is released
                  HCPSEGRS  when a normal segment table is released
                  HCPWLBRE  when a shadow segment table is released
                  and their clones

#### SEGTE Control Block Content

#### SEGTE DSECT

####

####

####

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      SEGTE          SEGMENT TABLE ENTRY
         ESA/390 mode Segment-Table Entry format
         THE SEGMENT TABLE DESCRIBES THE ADDRESS SPACE WHICH CONTAINS GUEST
         STORAGE.
         THERE IS ALSO A SEGMENT TABLE IDENTIFIED BY THE SYSTEM VMDBK, WHICH
         DESCRIBES THE SYSTEM VIRTUAL ADDRESS SPACE, WHICH IS ALWAYS ALLOCATED
         AS TWO FRAMES OF STORAGE.
         THERE IS ONE SEGMENT TABLE ENTRY FOR EACH MEGABYTE OF ADDRESS SPACE.
    0000    0 Signed       4 SEGENTRY       POINTER TO PAGE TABLE, PAGTB
                                            WITHIN THE PGMBK NOTE THAT
                                            ARCHITECTURE ALIGNS PAGE TABLES
                                            ON 64 BYTE BOUNDARIES BUT
                                            SOFTWARE RESTRICTS THE ALIGNMENT
                                            TO 256 BYTE BOUNDARIES BECAUSE OF
                                            THE USE OF THE LEFT- MOST 2 BITS
                                            IN THE RIGHTMOST BYTE. PAGE
                                            TABLES ARE IMBEDDED WITHIN
                                            PGMBK'S, THEREBY FORCING 4K
                                            ALIGNMENT.
              .... ....      SEGNULLM       X'80000000' Isolate null segment
                                            flag
              00FFFFC0       SEGPTOM        X'7FFFFFC0' Isolate page-table
                                            origin
              ..1. ....      SEGINVM        X'00000020' Isolate invalid bit
              ...1 ....      SEGCOMM        X'00000010' Isolate
                                            common-segment bit
              .... 1111      SEGPTLM        X'0000000F' Isolate page-table
                                            length
              00000004       SEGLENTH       *-SEGENTRY LENGTH OF ONE SEGMENT
                                            TABLE ENTRY
    0004    4 Signed       4 SEGNEXT (0)    NEXT SEGMENT TABLE ENTRY
    0000    0 Bitstring    1 SEGFLAG        SEGMENT ALLOCATION STATUS
                                            SEGINVAL MUST BE = 1.
              1... ....      SEGNULL        X'80' SEGMENT CANNOT BE ALLOCATED
                                            FOR GUEST STORAGE, IT IS NOT
                                            ADDRESSABLE BY THE USER. SEGINVAL
                                            MUST BE = 1.
         LEFTMOST BIT ARCHITECTED AS ZERO. RIGHTMOST 7 BITS COMPRISE BITS 1-7 OF
         THE 31 BIT REAL ADDRESS OF THE PAGE TABLE FOR THIS SEGMENT.
    0001    1 Bitstring    1 *              BITS 8-15 OF THE PAGE TABLE
                                            ADDRESS.
    0002    2 Bitstring    1 *              BITS 16-23 OF THE PAGE TABLE
                                            ADDRESS.
    0003    3 Bitstring    1 SEGSTAT        SEGMENT TABLE ENTRY STATUS
              1... ....      SEGWAIT        X'80' SEGMENT HAS TRANSLATION
                                            REQUESTS WAITING. SEGINVAL MUST
                                            BE = 1.
              .1.. ....      SEGTRANS       X'40' SEGMENT IS BEING TRANSLATED
                                            THIS BIT IS USED BY SOFTWARE TO
                                            SERIALIZE SEGMENT TRANSLATION.
                                            SEGINVAL MUST BE = 1.
              ..1. ....      SEGINVAL       X'20' SEGMENT TABLE ENTRY IS
                                            INVALID Note that SEGINVAL is
                                            also used for software purposes,
                                            with a different meaning, in
                                            "SEGTE"s which reside in segment
                                            table entry lists pointed to by
                                            STLBKs. These pseudo-SEGTEs are
                                            never attached in the hardware
                                            sense, and are never used
                                            directly in implicit hardware
                                            translations. They exist only to
                                            expedite the updating of the
                                            guest's real segment table during
                                            shared segment imbed processing.
              ...1 ....      SEGCOMMN       X'10' Common segment bit. NOTE:
                                            CP can not use this bit for
                                            software purposes in any SEGTE
                                            that could potentially be
                                            attached in the hardware sense
                                            (that is, any real, "live" SEGTE
                                            that resides in a segment table
                                            which is currently accessible by
                                            the hardware for use in any
                                            implicit translations), even if
                                            the SEGTE is invalid, due to a
                                            hardware problem on certain
                                            supported processors (3090 S
                                            models). However, SEGCOMMN *IS*
                                            used for software purposes, with
                                            a different meaning, in "SEGTE"s
                                            which reside in segment table
                                            entry lists pointed to by STLBKs.
                                            These pseudo-SEGTEs are never
                                            attached in the hardware sense,
                                            and are never used directly in
                                            implicit hardware translations.
                                            They exist only to expedite the
                                            updating of the guest's real
                                            segment table during shared
                                            segment imbed processing.
              .... 1111      SEGPTLNG       X'0F' Page table length (in units
                                            of 64 byte blocks, minus 1).
                                            Note: page table length bits only
                                            used when the SEGTE is valid
                                            (SEGINVAL bit is OFF) or in a
                                            "not yet referenced" state. If
                                            the SEGTE is invalid because the
                                            PGMBK has been paged out, these
                                            bits are re-used as status bits.
                                            Therefore, the page table length
                                            value must be restored from the
                                            copy saved in the PGMBK PGMPTLNG
                                            field whenever the SEGTE is
                                            validated (by turning SEGINVAL
                                            off) or cleared to a "not yet
                                            referenced" state
              .... 1...      SEGXSTOR       X'08' Used by CP to indicate that
                                            a PGMBK that resides on XSTORE
                                            supports pages that also reside
                                            on XSTORE. Note: This bit is only
                                            valid when SEGINVAL is on, and
                                            the PGMBK is paged out (bits 1-23
                                            of the SEGTE are non-zero and
                                            contain a valid PTRM "virtual
                                            address"). SEGXSTOR must not be
                                            used in a valid segment table
                                            entry, since it is one of the
                                            bits that make up the page table
                                            length field, SEGPTLNG.
              .... .1..      SEGPARTL       X'04' Used by CP to indicate that
                                            a SEGTE which has had its PGMBK
                                            paged out represents a partial
                                            segment with a less than full
                                            length page table. This bit will
                                            only be on in SEGTEs with paged
                                            out PGMBKs which represent
                                            partial segments at the end of
                                            the defined storage size of the
                                            address space (the last partial
                                            segment). Note: This bit is only
                                            valid when SEGINVAL is on, and
                                            the PGMBK is paged out (bits 1-23
                                            of the SEGTE are non-zero and
                                            contain a valid PTRM "virtual
                                            address"). SEGPARTL must not be
                                            used in a valid segment table
                                            entry, since it is one of the
                                            bits that make up the page table
                                            length field, SEGPTLNG. Mask to
                                            turn off SEGINVAL, SEGXSTOR,
                                            SEGPARTL, and all of the SEGPTLNG
                                            bits. (SEGXSTOR and SEGPARTL are
                                            bits in the SEGPTLNG half-byte.)
                                            These bits are all turned off
                                            together to ensure that they are
                                            turned off whenever SEGINVAL is
                                            turned off and the SEGTE
                                            validated, and to clear the rest
                                            of the SEGPTLNG bits for
                                            insertion of the real SEGTE page
                                            table length value, which is
                                            saved in the PGMBK field
                                            PGMPTLNG.
              0SEGSTAT       SEGINOFF       X'FFFFFFFF'-(SEGINVAL+SEGPTLNG)
                                            Mask to turn SEGINVAL and
                                            SEGPTLNG bits (including
                                            SEGXSTOR) all off at once. NOTE:
                                            The original page table length
                                            value must be restored (from
                                            PGMPTLNG) before the SEGTE is
                                            actually validated by storing the
                                            value generated using SEGINOFF
         LEFTMOST 2 BITS COMPRISE BITS 24-25 OF THE PAGE TABLE ADDRESS (6 BITS
         ARE APPENDED ON THE RIGHT TO FORM THE PAGE TABLE ADDRESS). LEFTMOST 2
         BITS USED BY SOFTWARE WHEN SEGMENT ENTRY IS INVALID. RIGHTMOST 6 BITS
         ARE ARCHITECTED AND USED AS DEFINED BELOW.
              00000028       SEGINON        (SEGINVAL+SEGXSTOR) Mask to turn
                                            SEGINVAL and SEGXSTOR on, and
                                            clear the remaining SEGPTLNG
                                            bits.
              .... 1111      SEGPTLMK       X'00000000'+SEGPTLNG Mask to
                                            isolate SEGPTLNG
              00FFFFBF       SEGTROFF       X'FFFFFFFF'-SEGTRANS MASK TO TURN
                                            SEGTRANS OFF
              00FFFF7F       SEGWTOFF       X'FFFFFFFF'-SEGWAIT MASK TO TURN
                                            SEGWAIT OFF
              00FFFF00       SEGPTRMK       X'7FFFFFFF'-(SEGWAIT+SEGTRANS+SEG
                                            INVAL+SEGCOMMN+SEGPTLNG) Mask to
                                            isolate or test for a PTRM
                                            "virtual address"
         The following maps the segment table entry in the System/370
         architecture.
              00FFFFF8       SEG3PTOM       X'00FFFFF8' Isolate page-table
                                            origin in S/370 architecture STE
              .... ...1      SEG3INVM       X'00000001' Isolate
                                            segment-invalid bit in S/370
                                            architecture STE
              .... ..1.      SEG3COMM       X'00000002' Isolate
                                            common-segment bit in S/370
                                            architecture STE
              .... .1..      SEG3PROM       X'00000004' Isolate
                                            segment-protection bit in S/370
                                            architecture STE
              .... ....      SEG3PTLM       X'F0000000' Isolate page-table
                                            length in S/370 architecture STE
              .... ...1      SEG3RSVM       X'0F000001' Reserved bits, must
                                            be 0 in any valid S/370
                                            architecture STE
    0003    3 Bitstring    1 SEGST370       SEGMENT TABLE ENTRY STATUS FOR
                                            370 NON-EXTENDED ARCHITECTURE
              .... .1..      SEG370PR       X'04' SEGMENT IS WRITE PROTECTED
              .... ...1      SEG370IV       X'01' SEGMENT IS INVALID END OF
                                            DEFINITION
              ...1 .1..      SEGSHIFT       20 BITS TO SHIFT RIGHT TO GET
                                            SEGMENT NUMBER FROM AN ADDRESS OR
                                            SHIFT LEFT TO GET STARTING
                                            SEGMENT ADDRESS FROM A SEGMENT
                                            NUMBER
              .1.. ....      SEGPTUNT       64 Number of bytes in a
                                            "page-table unit", the number of
                                            bytes in the smallest variation
                                            of the size of a page table.
              .... .11.      SEGPTUNS       6 Number of bits to shift left in
                                            order to multiply by SEGPTUNT.
              ...1 ....      SEGPXPTL       12+4 Bits to shift right an
                                            isolated page index to obtain a
                                            page- table length.
              .... 1.1.      SEGPXDSP       12-2 Bits to shift right an
                                            isolated page index to obtain the
                                            displacement into the page table
                                            of the applicable PTE.
         LEFTMOST 4 BITS COMPRISE BITS 16-19 OF THE PAGE TABLE ADDRESS
         RIGHTMOST 4 BITS DESCRIBE THE STATUS OF THE SEGMENT TABLE ENTRY
         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.

    SEGTB DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      SEGTB          SEGMENT TABLE
    0000    0 Signed       4 SEGORIGN (0)   Segment Table Origin
    0000    0 Bitstring    1 * (0)          First STE / SEGTE

    SEGTE Storage Layout

    *** SEGTE - SEGMENT TABLE ENTRY
    *
    *     +---------------------------+
    *   0 |         SEGENTRY          |
    *     +---------------------------+
    *
    *** SEGTE - SEGMENT TABLE ENTRY

    *** Overlay for SEGENTRY in SEGTE
    *
    *     +------+------+------+------+
    *   0 |:FLAG |//////|//////|:STAT | 4
    *     +------+------+------+------+
    *
    *** Overlay for SEGENTRY in SEGTE

    *** Overlay for SEGSTAT in SEGTE
    *
    *                          +------+
    *   0 ...                3 |:ST370| 4
    *                          +------+
    *
    *** Overlay for SEGSTAT in SEGTE

    *** SEGTB - SEGMENT TABLE
    *
    *
    *** SEGTB - SEGMENT TABLE

    SEGTE Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    SEGCOMM        0000 10
    SEGCOMMN       0003 10
    SEGENTRY       0000
    SEGFLAG        0000
    SEGINOFF       0003 0SEGSTAT
    SEGINON        0003 00000028
    SEGINVAL       0003 20
    SEGINVM        0000 20
    SEGLENTH       0000 00000004
    SEGNEXT        0004
    SEGNULL        0000 80
    SEGNULLM       0000 00
    SEGORIGN       0000
    SEGPARTL       0003 04
    SEGPTLM        0000 0F
    SEGPTLMK       0003 0F
    SEGPTLNG       0003 0F
    SEGPTOM        0000 00FFFFC0
    SEGPTRMK       0003 00FFFF00
    SEGPTUNS       0003 06
    SEGPTUNT       0003 40
    SEGPXDSP       0003 0A
    SEGPXPTL       0003 10
    SEGSHIFT       0003 14
    SEGSTAT        0003
    SEGST370       0003
    SEGTRANS       0003 40
    SEGTROFF       0003 00FFFFBF
    SEGWAIT        0003 80
    SEGWTOFF       0003 00FFFF7F
    SEGXSTOR       0003 08
    SEG3COMM       0003 02
    SEG3INVM       0003 01
    SEG3PROM       0003 04
    SEG3PTLM       0003 00
    SEG3PTOM       0003 00FFFFF8
    SEG3RSVM       0003 01
    SEG370IV       0003 01
    SEG370PR       0003 04

    This information is
    based on z/VM V4R3.0.
    Last updated on 30 Apr 2002 at 17:33:25 EDT.

    Copyright IBM Corporation, 1990, 2002