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

#### IFSNT

Prolog

Control Block Contents
IFSNT DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### IFSNT Prolog

     NAME       : HCPIFSNT
     DESCRIPTION: INTERPRETATION FACILITY SUBCHANNEL NUMBER TABLE
     DSECT      : IFSNT
     FUNCTION   : TO ALLOW THE MICROCODE TO DETERMINE IF A SIOF
                  INSTRUCTION ISSUED, UNDER SIE, BY THE V=R GUEST SHOULD
                  BE PASSED THROUGH OR CAUSE INTERCEPTION.
                  THE IFSNT IS A 16K TABLE ON A PAGE FRAME BOUNDARY. IT IS
                  CONTAINED IN FIXED, CONTIGUOUS REAL STORAGE. IT CONTAINS
                  ONE ENTRY (4 BYTES LONG) FOR EACH DEVICE THAT COULD BE
                  SUPPORTED UNDER I/O PASS THROUGH. IT IS ONLY APPLICABLE
                  FOR A 370 V=R GUEST. DEVICES WITH ADDRESSES 000 THRU
                  FFF ARE SUPPORTED UNDER I/O PASS THROUGH.
                  THE MICROCODE USES THE DEVICE ADDRESS OPERAND OF THE
                  SIOF INSTRUCTION TO INDEX INTO THE IFSNT. IF THE FIRST
                  BYTE OF THE ENTRY IS NON-ZERO, THE SIOF INSTRUCTION
                  IS ELIGIBLE TO BE PASSED THROUGH. THE FIRST BYTE THEN
                  CONTAINS THE LOGICAL PATH MASK (LPM) TO BE PLACED IN THE
                  OPERATION REQUEST BLOCK (ORB) CONSTRUCTED BY THE
                  MICROCODE. IF THE FIRST BYTE OF THE ENTRY IS ZERO, SIOF
                  MUST CAUSE INTERCEPTION.
                  THE SECOND BYTE IS RESERVED AND THE THIRD AND FOURTH
                  BYTES CONTAIN THE SUBCHANNEL NUMBER.
     LOCATED BY : THE ADDRESS OF THE REAL STORAGE IS CONTAINED IN SYSVRIFS
                  WHENEVER CP CAN ALLOCATE SUFFICIENT STORAGE.
                  WHEN A 370 V=R GUEST IS OPERATING UNDER I/O PASS THROUGH
                  THE ADDRESS OF THE INITIALIZED TABLE IS IN SIESNORG OF
                  THE BASE VMDBK.
     CREATED BY : HCPIOAIT, HCPIOAGS
     DELETED BY : HCPIOARC, HCPIOARS

#### IFSNT Control Block Content

#### IFSNT DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      IFSNT          INTERPRETATION FACILITY
                                            SUBCHANNEL NUMBER TABLE
    0000    0 Bitstring    1 IFSNTLPM       IF NON-ZERO, SIOF CAN BE PASSED
                                            THROUGH FOR THIS DEVICE. THIS
                                            BYTE CONTAINS LPM FOR MICROCODE
                                            BUILT ORB. IF ZERO, SIOF MUST
                                            CAUSE INTERCEPTION.
    0001    1 Bitstring    1 *              RESERVED FOR FUTURE IBM USE
    0002    2 Signed       2 IFSNTSNO       SUBCHANNEL NUMBER FOR THIS DEVICE
              IFSNTSNO       IFSNTLEN       4096*4 LENGTH OF IFSNT
              .... .1..      IFSNTFCT       4 NUMBER OF FRAMES NEEDED FOR THE
                                            IFSNT

#### IFSNT Storage Layout

    *** IFSNT - INTERPRETATION FACILITY SUBCHANNEL NUMBER TABLE
    *
    *     +------+------+-------------+
    *   0 |:NTLPM|//////|  IFSNTSNO   | 4
    *     +------+------+-------------+
    *
    *** IFSNT - INTERPRETATION FACILITY SUBCHANNEL NUMBER TABLE

#### IFSNT Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    IFSNTFCT       0002 04
    IFSNTLEN       0002 IFSNTSNO
    IFSNTLPM       0000
    IFSNTSNO       0002

This information is based on z/VM V4R3.0. Last updated on 30 Apr 2002 at 16:37:22 EDT.
Copyright IBM Corporation, 1990, 2002