CONTROL PROGRAM ASSIST (CP ASSIST) The following information describes the CP assist functions that are
invoked directly or indirectly by the VM/310 Control program. CP assist is part of ECPS. CP assist is hardware that assists VM/310 Control Program functions with new instructions.
Except for the functions initiated by VM/310 SVCs, all CP assist
functions are System/310 instructions. The CP assist instructions are six bytes long and are in an SS format. The format is:
o 8 16 20 32 36
T
E6 xx I B1 D1 B2 D2 E6 is the first byte of the op code for all CP assist instructions xx is the second byte of the op code and is an cp code extension
that is unique for each instruction.
Each instruction has two operands that are effective addresses
calculated from the B1D1 and B2D2 values in the normal System/310 way.
The specific instruction determines whether these operands are
data, addresses, or not used.
The following table summarizes the operation codes, instruction names, and descriptions of the CP assist instructions:
Trace Table VM/310 CP Q-E I!!§!fY£!!.Q!! E600 Yes FREE Get free storage space E601 Yes FRET Return free storage space E602 No PTRLK Lock a page E603 No PTRUL Unlock a page E604 No DECCWO Decode subsequent CCW commands E605 No UNTFR Free CCW storage E606 No SCNVU Locate virtual I/O control blocks E601 No DSP1 Dispatch a block or a virtual
machine -full function E608 No TRANBRNG Test page status E609 No TRANLOCK Test page status and lock E60A No ZAPSEGS Invalidate segment table E60B No ZAPPAGE Invalidate page table E60C No DECCW1 Decode first CCW command E60D No DSPO Main entry to dispatcher E60E No SCNRU Locate real I/O control blocks E60F No CCWGENRL Common CCW co •• and processing E610 No UNTRN Untrans1ate CSI 1-416 IBM VM/370 System Logic and Problem Deteraination--Volu.e 1

I I 1 1 Trace Table V8/370 ,CP QE E611 Yes DSP2 Dispatch a block or a virtual
machine -abbreviated function
E612 No STECPSV8 Store V8/370 ECPS identification
E613 No SHARED Locate changed shared page OA08 Yes LINK V8/370 Control program SVC LINK OAOC Yes RETURN VM/370 Control program SVC RETURN The following example shows how to identify CP assist instructions in
assembly listings. DftKFREE USING DS
DS DftKFREE,R15 alV386918 alV386198 ! E600F718F64B DC STM LR alV386198 X'E600',S(SUBTABLE,BYTBL-1) ***V386198 00218700 00218800 00219200 00219300 00220000 00221000 1 RO,R15,FREESAVE ••••••••• I • R12,R15 IV386198 1-.------------------------------------------------- -------------------------- I • I CP assist instruction is CP assist function exe- I identified by E6 op code cutes software instruc- 1 tions identified by 1 sign. :-Bote: Instructionsmarked-with-i-incolUmn64 may not actually be executed I if-CP assist is enabled. For example, register contents may not be stored I in temporary save areas and certain additional constants aay be referenced. I the functional equivalent of the group of instructions aarked by I the is performed by CP assist. , DMKCPI ENTRY POINT LIST: In the module DMKCPI is a list of entry points that-contaIn -the-control program assist instructions (X'E6' op code).
This list has the label CPATABLE. This list is shown in the following example: Entry CP Assist CPATABLE DS OF DC V (DMKFREE) E600 DC V (DftKFRET) E601 DC v (DMKPTRLK) E602 DC V (DMKPTRUL) E603 DC V (DMKCCWO) E604 DC V (DMKUNTFR) E605 DC V (DMKSCNVU) E606 DC V (DMKDSP1) E607 DC V (D8KCCWB 1) E608 DC V (DMKCCWB2) E608 DC V (DMKCCWB3) E608 Appendix A: VM/370 Extended Control-Program Support 1-417