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Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM. |
SEGTE
Control Block Contents
SEGTE DSECT
SEGTB DSECT
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
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
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
...1 .... SEGCOMMN X'10' Common segment bit.
.... 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.
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
...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 0 * (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 V4R1.0.
Last updated on 5 Jun 2001 at 16:32:09 EDT.
Copyright IBM Corporation, 1990, 2001