interruption takes place for a privileged
operation exception (1. B. 1 ).
6.If an access exception exists for a store access
made with thePSW key to the location
designated by the first-operand address,
execution of this function ends, and a program
interruption is taken for the access exception
found (1.B.2).
7. The old value of byte0 of the virtual PSW is
stored at the first-operand logical address. The
updated virtualPSW is stored as the new
virtualPSW with a key of zero (2).
Execution of this function ends with completion
of theSTORE THEN AND SYSTEM MASK
instruction.
Figure 17 summarizes the fields used.STORE THEN OR SYSTEM MASK The STORE THEN OR SYSTEM MASK
instruction is executed for a virtual machine if the
virtual-machine assist is activated for System/370
instructions, unless (1) a virtual-machine
interruption may follow, (2) the first operand or
some pertinentVM/370 control field cannot be
accessed, or (3) thePER mask or the DAT bit of
the virtualPSW would be changed.
If the shadow-table-bypass assist is not installed,
the store-then-OR-system-mask function of the
virtual-machine assist is invoked each time aCPU attempts to execute a STORE THEN OR SYSTEM
MASK instruction when the problem-state bit of
the realPSW is one. If the shadow-table-bypass
assist is installed, the store-then-OR-system-mask
function of the virtual-machine assist may be. invoked only from the STOSM function of the
shadow-table-bypass assist. Execution of this
function consists in performing the following steps:
1. If bits0-3 of control register 6 are not 10XO binary, execution of this function ends, a
program interruption takes place for a
privileged-operation exception, and execution
of theSTORE THEN OR SYSTEM MASK
instruction is suppressed (l.A.l).
FieldControl Address Offset No. of
2. The wordMICVPSW, which contains the
address of the virtualPSW, is fetched with a
key of zero. Execution ends if an addressing
condition is encountered (l.A.2).
3. The first halfword ofVMPSW, which contains
the virtualPSW, is fetched with a key of zero.
Execution ends if an addressing condition is
encountered (l.A.3).
4. A new first byte for the virtualPSW is
computed by taking the logicalOR of the
immediate field (12) of the instruction and byte
o of the virtualPSW fetched. If the virtual PSW is in the EC mode (bit 12 is one) and if
the replacement of byte0 of the virtual PSW by the new byte 0 would change any of the bits
in bit positions0-5 from zero to one, execution
of this function ends. Execution also ends if
bit0 of MICVPSW is one and if the
replacement of byte0 of the virtual PSW by
the newPSW would change any bit from zero
to one. Ending of execution invokes the store
then-OR-system-mask function of the expanded
virtual-machine assist if that assist is installed.Otherwise, ending of execution causes a
program interruption to be taken for a
privileged-operation exception (l.A. 4).
5. The second halfword of the instruction is
fetched. If an access condition is encountered,
execution of this function ends, and a program
interruption takes place for a privileged
operation exception(1.B.O. 6. If an access exception exists for a store access
made with thePSW key to the location
designated by the first-operand logical address,
execution of this function ends, and a program
interruption takes place for the access
exception found (1.B.2).
7. The old value of byte0 of the virtual PSW is
stored at the first-operand logical address. The
updated virtualPSW is stored with a key of
zero as the new virtualPSW. Execution of this
function ends with the completion of theSTORE THEN OR SYSTEM MASK instruction
(2).
Figure 18 summarizes the fields used.
Name Block Type (Hex) BytesContents MICVPSW MICBLOK Real 8 4 Address of VMPSW VMPSW VMBLOK Real 0 2 Virtual PSW bits 0-15 Operand 1 -Logical -1 Old system mask
Figure 17. Fields Used inSTORE THEN AND SYSTEM MASK
22 Virtual-Machine Assist and Shadow-Table-Bypass Assist
operation exception (1. B. 1 ).
6.
made with the
designated by the first-operand address,
execution of this function ends, and a program
interruption is taken for the access exception
found (1.B.2).
7. The old value of byte
stored at the first-operand logical address. The
updated virtual
virtual
Execution of this function ends with completion
of the
instruction.
Figure 17 summarizes the fields used.
instruction is executed for a virtual machine if the
virtual-machine assist is activated for System/370
instructions, unless (1) a virtual-machine
interruption may follow, (2) the first operand or
some pertinent
accessed, or (3) the
the virtual
If the shadow-table-bypass assist is not installed,
the store-then-OR-system-mask function of the
virtual-machine assist is invoked each time a
MASK instruction when the problem-state bit of
the real
assist is installed, the store-then-OR-system-mask
function of the virtual-machine assist may be
shadow-table-bypass assist. Execution of this
function consists in performing the following steps:
1. If bits
program interruption takes place for a
privileged-operation exception, and execution
of the
instruction is suppressed (l.A.l).
Field
2. The word
address of the virtual
key of zero. Execution ends if an addressing
condition is encountered (l.A.2).
3. The first halfword of
the virtual
Execution ends if an addressing condition is
encountered (l.A.3).
4. A new first byte for the virtual
computed by taking the logical
immediate field (12) of the instruction and byte
o of the virtual
the replacement of byte
in bit positions
of this function ends. Execution also ends if
bit
replacement of byte
the new
to one. Ending of execution invokes the store
then-OR-system-mask function of the expanded
virtual-machine assist if that assist is installed.
program interruption to be taken for a
privileged-operation exception (l.A. 4).
5. The second halfword of the instruction is
fetched. If an access condition is encountered,
execution of this function ends, and a program
interruption takes place for a privileged
operation exception
made with the
designated by the first-operand logical address,
execution of this function ends, and a program
interruption takes place for the access
exception found (1.B.2).
7. The old value of byte
stored at the first-operand logical address. The
updated virtual
zero as the new virtual
function ends with the completion of the
(2).
Figure 18 summarizes the fields used.
Name Block Type (Hex) Bytes
Figure 17. Fields Used in
22 Virtual-Machine Assist and Shadow-Table-Bypass Assist