Programming Interface Information:
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SEGTE
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 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. 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 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. 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. 00FFFFD0 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 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" 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 LEFTMOST 4 BITS COMPRISE BITS 16-19 OF THE PAGE TABLE ADDRESS RIGHTMOST 4 BITS DESCRIBE THE STATUS OF THE SEGMENT TABLE ENTRY END OF DEFINITION 00000014 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 00000040 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. 00000006 SEGPTUNS 6 Number of bits to shift left in order to multiply by SEGPTUNT. 00000010 SEGPXPTL 12+4 Bits to shift right an isolated page index to obtain a page- table length. 0000000A SEGPXDSP 12-2 Bits to shift right an isolated page index to obtain the displacement into the page table of the applicable PTE. 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) in length. For guest primary address spaces, the segment table may be imbedded in the VMDBK when the maximum primary address space addressability required is 32MB or less. For guest primary address spaces from 33MB to 1024 MB, or for non-primary virtual address spaces of 1024MB 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 1024MB 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 1024MB in size, two contiguous pages are allocated. If the maximum virtual addressability required is less than 2047MB, the second page may be in use for GUESTPERM type VMDBK free storage. The SYSTEM virtual address space is always defined to be 2048MB in size and its segment table is always allocated as two 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 CONTROL REGISTER 1 CONTROL REGISTER 7 PGMSEGTE field of the associated PGMBK (if any) VMDPSTD field of HCPVMDBK 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 | | * +---------------------------+ | * 8 | | * = SEGNEXT = * | | * +-------------------------------------------------------+ * *** 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
(contains links to field and bit definitions)Symbol Dspl Value -------------- ---- -----SEGCOMM 0000 10
SEGCOMMN 0003 10
SEGENTRY 0000
SEGFLAG 0000
SEGINOFF 0003 00FFFFD0
SEGINON 0003 00000028
SEGINVAL 0003 20
SEGINVM 0000 20
SEGLENTH 0000 00000004
SEGNEXT 0004
SEGNULL 0000 80
SEGORIGN 0000
SEGPARTL 0003 04
SEGPTLM 0000 0F
SEGPTLMK 0003 0F
SEGPTLNG 0003 0F
SEGPTOM 0000 00FFFFC0
SEGPTRMK 0003 00FFFF00
SEGPTUNS 0003 00000006
SEGPTUNT 0003 00000040
SEGPXDSP 0003 0000000A
SEGPXPTL 0003 00000010
SEGSHIFT 0003 00000014
SEGSTAT 0003
SEGST370 0003
SEGTRANS 0003 40
SEGTROFF 0003 00FFFFBF
SEGWAIT 0003 80
SEGWTOFF 0003 00FFFF7F
SEGXSTOR 0003 08
SEG370IV 0003 01
SEG370PR 0003 04
Last updated on 3 Aug 1999 at 12:31:01 EDT.
Copyright IBM Corporation, 1990, 1999