CP Interruption Handling Interruption processing occurs within the CP environaent. Bore than 30 aodules control the process of interrupting events brought about by CP or virtual machine activity. Each aodule handles a particular I/O device or class or a function of CP, (for exaaple: tiaers, paging. SVCs)@ For an overview of interruption handling, see Figure 14. Program Interruption Program interruptions occur in two states. If the CPU is in the
supervisor state, the interruption indicates a systea failure in the CP nucleus and causes a system abnoLaal If the cpo in the problem state, a virtual machine is in execution. If the prograa
interruption indicates that the Dynaaic Address Translation (DAT) feature has an exception, a virtual machine issued a privileged
instruction, or a protection exception occurred for a shared segment
systea, CP takes control and performs any required processing to satisfy
the exception. Usually, the interruption is not apparent to the virtual
aachine. Most other program interruptions result from virtual aachine
processing and. are reflected to the virtual machine for handling. When a prograa interruption occurs, the prograa interruption handler (DMKPRG) is entered. Program interruptions can result froa: • Normal paging requests • A paging request by a virtual aachine in EC mode (virtual relocate
aode) • Privileged instructions • Program errors For information about paging requests, see "Allocation Banagement" in
this section. Privileged Instructions If a program interruption is by the virtual machine issuing a
privileged instruction when it 1S running in supervisor state, DBKPRVLG obtains the address of the privileged instruction and determines the
type of operation requested. If the virtual machine was running in
problem state, the interruption is reflected back to the virtual
lIachine. I/O PRIVILEGED INSTRUCTIONS DMKPRVLG transfers control to the (DMKVS lEX) • virtual I/O executive program 1-46 IBM VM/370 System Logic and Problem Determination--Volume 1

I I TYPE MODULE I SiC I External Aachine Check I/O Prograll Check DMKSVCIN DMKPSAEI DMKMCHIN DMKIOSIN DMKPRGIN Interrupt Handler Modules , I Interrupt Froll Action/Module Unknown channel Unsolicited device end
and for:
Console 3270s on bisync lines
Local 3270, 3158, and 3066 consoles Unit record, real spooling
Solicited device end
Channel error
Monitor tape I/O operation
Dedicated device error - DASD Dedicated device error -Tape 3270 bisync line and channel errors
R
ecoverab Ie Unrecoverable /0 Interrupt Handler (DMKIOS) Actions
Reason for Prograll Check
Bor.al paging Paging - virtual machine in EC lIode
Supervisor State Privileged instruction DIAGNOSE Tillers Virtual Machine I/O console
unit record, virtual spooling
Ignored - DMKDSPCH Build rOBLOR DMKCBSIB DMKRGA or DMKRGB DMKGRF DMKRSPEI DMKSTKIO D!KCCHBT DMK!OBIO DMKDASER D!KTAPER DMKBSG D!KSTKIC DMKIOERR Module DMKPTRAN DMKVAT D!KDMP DMKPRVLG DMKHVC DMKTMR DMKVSIEX DMKVCBEI D!!KVSPEI Prograll Check Interrupt Handler (D!!KPRG) Actions
Figure 14. Overview of Interruption Handling NOB-I/O PRIVILEGED INSTRUCTIONS I I I D!!KPRVLG siaulates valid non-I/O privileged instructions and returns
control to DMKDSPCH. For invalid non-I/O privileged instructions, the
routine sets an invalid interruption code and reflects the interruption
to the virtual aachine. For the privileged instructions (SCK, SCKC, STCKC, SPT, and STPT) that affect the TOD clock, CPU tiller, and TOD clock coaparator, control is transferred to D!!KT!!R by D!!KPRVLG. Other instructions that are sillulated are LPSW, SS!!, SSK, ISK, IPTE, and DIAGNOSE. CP Introduction 1-47