z/VM: CP Commands and Utilities Reference - z/VM - IBM

Messages
HCP002E Invalid operand - operand
HCP026E Operand missing or invalid
4. PAGEX is used by the following IBM operating systems:
VSE/ESA*
GCS
5. If the virtual configuration executes a SIGP Set-Architecture instruction, the
pseudo-page-fault facility is reset.
6. SET PAGEX ON may not be issued when the asynchronous page-fault
handshaking facility for the host-primary address space is in effect (when the
VERSION=2 parameter of the PFAULT TOKEN macro has been specified).
Pseudo-Page-Fault Interruption
A pseudo-page-fault (PPF) interruption is a program interruption with interruption
code X'0014'. There are two types of PPF interruptions, initial and completion.
When PPF interruptions are enabled and a guest instruction encounters a CP page
fault which can not be resolved immediately, a PPF initial interruption is presented
to the virtual CPU. This allows the guest supervisor to suspend the running thread
and dispatch another. For each initial interruption, a completion interruption
specifying the same fault address is presented to the same virtual CPU when the
page fault has been resolved. This signals the guest supervisor to unblock the
affected thread.
If the virtual CPU is disabled for PPF interruptions when a page fault occurs, the
fault is handled synchronously; that is, execution of the virtual CPU is suspended
until the fault is resolved. If the virtual CPU is disabled for PPF interruptions when a
previous asynchronous page fault is completed, the completion interruption remains
pending until the virtual CPU enables.
PPF interruptions are enabled on a virtual CPU when all of the following are true:
v PAGEX is set ON for the virtual machine.
v The PSW is enabled for I/O interruptions. (PSW bit 6 is one.)
In addition, if the virtual machine is in z/Architecture mode, PPFs are presented
only for faults on guest-real addresses below 2 GB. Faults on higher addresses are
handled synchronously, as if PPF interruptions were disabled.
When a PPF interruption is presented, an interruption parameter is stored at guest
real locations 144-147 (X'90'-X'93'), as follows:
v Bit 0 is zero for a PPF initial interruption, or one for a PPF completion
interruption.
v Bits 1-31 are the guest-real starting address of the page on which the fault
occurred. (Bits 20-31 are zero.)
HCP1404E Asynchronous page-fault handshaking
for the host-primary space is already in
effect. PAGEX cannot be activated.
SET PAGEX
Chapter 2. CP Commands 1311