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

IASIT

Prolog  

Control Block Contents  
   IASIT DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  


IASIT Prolog

 Name       : HCPIASIT
 Description: Internal-Address-Space-Identification
              Token
 DSECT      : IASIT
 Function   : This DSECT maps an i-ASIT, which is CP's internal
              identification of an address space.
 Located by : Any task needing an identification of an address
              space.  Some important fields which contain i-ASITs
              are:
              RSANASIT i-ASIT for "null" address space.
 Created by : HCPSIT%I when translating various representations of
              address spaces into i-ASITs.
 Deleted by : Any task which no longer needs the representation.
 Notes      :
  An i-ASIT is an eight-byte token, doubleword aligned, and  *
  serves as a task's internal representation of a particular *
  address space.  An i-ASIT contains information designating *
  which address space, information defining the task's       *
  "capability" to access the address space, and information  *
  defining the method of translating addresses for that      *
  task.  Since it contains more information than just what   *
  is necessary to identify an address space, an i-ASIT       *
  cannot be directly compared to another i-ASIT to determine *
  if the same space is designated.  A service routine (as    *
  provided by the HCPCMPIA macro) must be used for i-ASIT    *
  comparison purposes.                                       *
                                                             *
  The capabilities represented in an i-ASIT are the          *
  following:                                                 *
                                                             *
    - r-access vs. i-access                                  *
    - Read/write vs. read/only permission                    *
    - For guest instruction-stream references, whether       *
      guest prefixing, guest low-address protection,         *
      and guest fetch-protection override apply.             *
                                                             *
  Translation of a guest real address into a host real       *
  address is affected by whether or not the address space is *
  the user's base address space, and whether or not the      *
  user's reference is a primary-space or secondary-space     *
  reference.  Prefixing, low-address protection, and         *
  fetch-protection override apply only when the space is the *
  base, and when the access is a primary-space or            *
  secondary-space reference.                                 *
                                                             *
  An i-ASIT must be certified before it can be used for any  *
  purposes.  A certified i-ASIT is one that meets the        *
  following criteria:                                        *
                                                             *
     - The ASTE sequence number in the i-ASIT matches        *
       the ASTE sequence number in the ASTE (i- or r-access) *
       *or*                                                  *
     - ASCSEQNO <= ASITSN <= ASTSN          (r-access)       *
                                                             *
  The i-ASIT certification function is provided by either    *
  the HCPASMCI entry point or the HCPACERT macro (to be used *
  only in cases where performance is a major concern, or the *
  routine cannot call another routine which uses PFXTMPSV).  *
  Other services which process i-ASITS, such as HCPCMPIA     *
  and HCPCHCR7, handle certification of i-ASITs internally.

 

IASIT Control Block Content


IASIT DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      IASIT          Internal-Address-Space-Identifica
                                        tion
0000    0 Address      4 IASASTEO (0)   Bits 1-25 are the ASTE origin
                                        NOTE: This field may ONLY be used
                                        in a certified i-ASIT, otherwise,
                                        it may point to an ASTE which has
                                        no relation to the i-ASIT.
          00FFFFC0       IASASTOM       X'7FFFFFC0' Mask to apply to
                                        IASASTEO to isolate ASTE origin.
          .... ..1.      IASREADM       X'00000002' Mask for read-only
                                        bit
          .... ...1      IASFPRVM       X'00000001' Mask for
                                        force-private-space bit
0000    0 Bitstring    1 * (3)          First 3 bytes are ASTE origin
0003    3 Bitstring    1 IASFLAGS       Authorization/capability flags
          .... .1..      IASRACC        X'04' When set, task has r-access
                                        to the address space.
          .... ..1.      IASREAD        X'02' When set, task has
                                        read-only access to space.
          .... ...1      IASFPRIV       X'01' Force-Private-Space bit
                                        When set, guest prefixing,
                                        low-address protection, and
                                        fetch-protection override do not
                                        apply. When not set, they do
                                        apply.
0004    4 Signed       4 IASASTSN       I-ASIT ASTE sequence number. It
                                        is compared with ASTE sequence
                                        number in ASTE.
          00000008       IASLEN         *-IASIT Length in bytes of an
                                        i-ASIT
          00000001       IASSIZE        (IASLEN+7)/8 Size in doublewords
                                        of an i-ASIT

 

IASIT Storage Layout

          
*** IASIT - Internal-Address-Space-Identification
*
*     +--------------------+------+---------------------------+
*   0 |////////////////////|:FLAGS|         IASASTSN          |
*     +--------------------+------+---------------------------+
*   8
*
*** IASIT - Internal-Address-Space-Identification

 

IASIT Cross Reference

Symbol         Dspl Value
-------------- ---- -----
IASASTEO       0000
IASASTOM       0000 00FFFFC0
IASASTSN       0004
IASFLAGS       0003
IASFPRIV       0003 01
IASFPRVM       0000 01
IASLEN         0004 00000008
IASRACC        0003 04
IASREAD        0003 02
IASREADM       0000 02
IASSIZE        0004 00000001

This information is based on z/VM V4R1.0.
Last updated on 5 Jun 2001 at 13:53:49 EDT.
Copyright IBM Corporation, 1990, 2001