Note: Because all the preceding conditions
involve the value [etched in step 4, the priority
of step 15 (2. C. 9.B) is necessarily lower than
that of step 4, regardless of the rules based on
priority indicators.
If execution ends, a real supervisor-call
interruption takes place.
16. If the supervisor-call interruption code is 76
(4C hex), execution ends, and a real
supervisor-call interruption takes place (2.D).
17. The oldPSW and interruption code are stored,
with a key of zero, in20 hex and 88 hex of
virtual page0 as appropriate to the mode of the
Shadow-Table Validation
When the real page-table entry used for dynamic
address translation is invalid and the shadow
table-validation function is active, the correct, valid
entry value derived from the virtual and real
translation tables is placed in that page-table entry.
However, this validation function is not performed
if any exception condition is found in fetching or
using the corresponding real or virtual translation
table entries. current virtual PSW. The stored values are the
If the shadow-table-bypass assist is not installed,
the shadow-table-validation function of the
virtual-machine assist is invoked whenever a
program interruption is about to take place for a
page-translation condition encountered outside the
shadow-table-validation function itself. If the
shadow-table-bypass assist is installed, the
shadow-table-validation function may be invoked
only from the page-fault-reflection function of the
shadow-table-bypass assist. If this function
successfully validates the shadow-table page entry
which caused the page-translation condition,
instruction execution that was in progress is
resumed or restarted. Otherwise, a program
interruption takes place for the original page
translation condition or, in some cases, for an
addressing condition encountered in performing the
shadow-table-validation function. The execution of,J' ;,0-: current virtual PSW, ILC, and SVC-number values updated by the condition code, program
mask, andfrom the real.", PSW. 'The virtual PSW is stored as the .", ---aIiTeiit virtual PSW in real storagef1ne .;', .()' and I instruction-address parts of the new virtual
.' \PSW replace the corresponding "" real The--problem'-state bit of the new vlrtuafpSW is placed in bit .. 9i...real control register function and"-a new virtual instruction is fetched
with the new realPSW (3).
Figure 19 summarizes the fields used.
FieldControl Address Offset No. of
Name Block Type (Hex) BytesContents MICRSEG MICBLOK Real 0 4 Address of real
segment tableMICVPSW MICBLOK Real 8 4 Address of VMPSW VMPSW VMBLOK Real 0 8 Virtual PSW SEGPAGE SEG Real 0 4 First real segment
TABLE table entryPAGCORE PAG Real 0 2 Address of PSA of
TABLE virtual machine
-PSA of Real' 20 8 Old SVC PSW virtual
Rea 11 -machine60 8 New SVC PSW - Real
1
88 4 Interruption code
2
1 This real address is obtained by the address translation
performed in steps 6 through 12 without using control
registers0 and 1.
2 This field is stored only when oldSVC PSW is in EC mode.
Figure 19.Fields Used in SUPERVISOR CALL
24 Virtual-Machine Assist and Shadow-Table-Bypass Assist
involve the value [etched in step 4, the priority
of step 15 (2. C. 9.B) is necessarily lower than
that of step 4, regardless of the rules based on
priority indicators.
If execution ends, a real supervisor-call
interruption takes place.
16. If the supervisor-call interruption code is 76
(4C hex), execution ends, and a real
supervisor-call interruption takes place (2.D).
17. The old
with a key of zero, in
virtual page
Shadow-Table Validation
When the real page-table entry used for dynamic
address translation is invalid and the shadow
table-validation function is active, the correct, valid
entry value derived from the virtual and real
translation tables is placed in that page-table entry.
However, this validation function is not performed
if any exception condition is found in fetching or
using the corresponding real or virtual translation
table entries.
If the shadow-table-bypass assist is not installed,
the shadow-table-validation function of the
virtual-machine assist is invoked whenever a
program interruption is about to take place for a
page-translation condition encountered outside the
shadow-table-validation function itself. If the
shadow-table-bypass assist is installed, the
shadow-table-validation function may be invoked
only from the page-fault-reflection function of the
shadow-table-bypass assist. If this function
successfully validates the shadow-table page entry
which caused the page-translation condition,
instruction execution that was in progress is
resumed or restarted. Otherwise, a program
interruption takes place for the original page
translation condition or, in some cases, for an
addressing condition encountered in performing the
shadow-table-validation function. The execution of
mask, and
.' \
with the new real
Figure 19 summarizes the fields used.
Field
Name Block Type (Hex) Bytes
segment table
TABLE table entry
TABLE virtual machine
-
Rea 11 -machine
1
88 4 Interruption code
2
1 This real address is obtained by the address translation
performed in steps 6 through 12 without using control
registers
2 This field is stored only when old
Figure 19.
24 Virtual-Machine Assist and Shadow-Table-Bypass Assist