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Programming Interface Information:
This information is NOT intended to be
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