Programming Interface Information:
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used as Programming Interfaces of z/VM. |
SCABK
Control Block Contents
SCABK DSECT
Cross Reference (Contains links to field and bit definitions)
SCABK Prolog
Name : HCPSCABK Description: System Control Area for Interpretive Execution DSECT : SCABK Function : Map SCA for SIE virtual MP support Located by : VMDISCAA in all VMDBKs of the virtual configuration points to label SCASTART in this block. *** NOTES : VMDISCAA does NOT point to the front of the block. Created by : HCPBIESC Deleted by : HCPBIESC, HCPBIESR Serialized : The existence of the SCABK, and the contents of its pointer, VMDISCAA, are serialized by console function mode. SCAIPLOK is a formal lock. SCAMCN is updated under Console-Function Mode. SCAXCALL is updated either in Console-Function Mode, or by compare-and-swap exclusive from CFM. Comments : The SCABK maps the architected System Control Area for SIE, used in support of virtual multiprocessing. In addition to the architected block, the SCABK contains a header for CP use. The size of the block is variable, depending on the maximum CPU address defined in the virtual configuration. Because architecture requires a quadword boundary for the SCA, an extra doubleword is allocated, and the SCABK is installed beginning either 0 or 8 bytes into the free-storage area, as needed to satisfy the boundary requirement. To simplify storage allocation, the actual start of the block is saved in the CP prefix portion of the SCABK. The SCABK is located by pointer VMDISCAA in all VMDBKs of the virtual configuration. VMDISCAA points to the architected SCA, at label SCASTART, NOT to the CP header at the front of the SCABK, nor to the start of the free-storage block.
SCABK Control Block Content
SCABK DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure SCABK System Control Area for Interpretive Header for CP software use Notes : This area must be an integral number of doublewords. 0000 0 Address 4 SCAFSADR Start address of containing free storage block 0004 4 Signed 2 SCAMXCPU Maximum virtual CPU address in configuration 0006 6 Signed 2 * Reserved for future IBM use 0008 8 Signed 4 * (2) Reserved for future IBM use Architected System Control Area 0010 16 Bitstring 8 SCASTART (0) *** True SCA begins here *** 0010 16 Bitstring 1 SCAIPLK0 (0) Redefinition of IPTE Interlock (below): 1... .... SCAIPLKH X'80' IPTE interlock is held 0010 16 Dbl-Word 8 SCAIPLOK (3) IPTE interlock 0028 40 Dbl-Word 8 * Reserved for future IBM use 0030 48 Dbl-Word 8 * (2) Reserved for future IBM use 0040 64 Dbl-Word 8 SCAMCN Mask of valid virtual CPU addrs for SIGP interpretation (may be a subset of defined virtual CPUs) 0048 72 Dbl-Word 8 * Reserved for future IBM use 0000000B SCAFSIZE (*-SCABK+15)/8 Fixed size for free-storage allocation (includes CP header, architected header, and an extra doubleword to allow quadword alignment) There are two versions of the SIGP entry (CPU descriptor). Which entry to use is dependent on the mode of the host. Thus the SCACPU portion of the SCABK must be different for an ESAME mode host CP than it is for an ESA/390 mode host CP and there are two versions of it below. When making modifications, be sure to consider both versions. This is the ESA/390 host CP version 0050 80 Bitstring 8 SCACPU (0) CPU descriptor (one slot per virtual CPU addr): 0050 80 Signed 4 SCAXCWRD (0) Word for Compare-and-Swap 0050 80 Bitstring 1 * Reserved for future IBM use 0051 81 Bitstring 1 SCAXCALL External-call state: 1... .... SCAXCPND X'80' ..external call pending ..11 1111 SCAXCCPU X'3F' ..mask to isolate sending CPU addr 0052 82 Bitstring 1 * (2) Reserved for future IBM use 0054 84 Address 4 SCASDESC Pointer to state description, or zero if virtual CPU not defined 0058 88 Signed 4 * (2) Reserved for future IBM use 00000010 SCACLEN *-SCACPU Length of one SCACPU entry 00000002 SCACSIZE (SCACLEN+7)/8 Size in doublewords 00000001 SCACPUSD SCACPUSB-3 Shift count to convert CPU addr to number of doublewords (SCACSIZE = 2**SCACPUSD)
SCABK Storage Layout
*** SCABK - System Control Area for Interpretive * * +---------------------------+-------------+-------------+ * 0 | SCAFSADR | SCAMXCPU |/////////////| * +---------------------------+-------------+-------------+ * 8 |///////////////////////////////////////////////////////| * +-------------------------------------------------------+ * 10 | | * = SCAIPLOK = * | | * +-------------------------------------------------------+ * 28 |///////////////////////////////////////////////////////| * +-------------------------------------------------------+ * 30 |///////////////////////////////////////////////////////| * |///////////////////////////////////////////////////////| * +-------------------------------------------------------+ * 40 | SCAMCN | * +-------------------------------------------------------+ * 48 |///////////////////////////////////////////////////////| * +------+------+-------------+---------------------------+ * 50 |//////|:XCALL|/////////////| SCASDESC | * +------+------+-------------+---------------------------+ * 58 |///////////////////////////////////////////////////////| * +-------------------------------------------------------+ * 60 * *** SCABK - System Control Area for Interpretive
SCABK Cross Reference
Symbol Dspl Value -------------- ---- ----- SCACLEN 0058 00000010 SCACPU 0050 SCACPUSD 0058 00000001 SCACSIZE 0058 00000002 SCAFSADR 0000 SCAFSIZE 0048 0000000B SCAIPLKH 0010 80 SCAIPLK0 0010 SCAIPLOK 0010 SCAMCN 0040 SCAMXCPU 0004 SCASDESC 0054 SCASTART 0010 SCAXCALL 0051 SCAXCCPU 0051 3F SCAXCPND 0051 80 SCAXCWRD 0050
Last updated on 5 Jun 2001 at 16:27:25 EDT.
Copyright IBM Corporation, 1990, 2001