DMKVCA, VCASIOB ---netected-Interruptions are presented to users via stacked IOBLOKs and DMKSTKIO. CTCA TIO activity is determined by examining Y-side information to
determine mode and activity. DMKVCASH ---cTci-HIO and HDV is processed by determining the conition code to
present and whether the Y-side should be notified. CTCA process results from RESET xxx or SYSTEM RESET commands. The CTC! status is reset but the CTCAs are not uncoupled. DMKVCARS ---Uncoupling CTC! is achieved in the VDEVBLOK (VDEVNRDY flag) idle CTC!
plus an invoked DETACH xxx or user LOGOFF. Return to calling
routine. SCHEDULING I/O FOR CP AND THE VIRTUAL MACHINE Entered via SVC. Entry point indicate a CP I/O event as indicated in
the IOBLOK. For start request, increment the SIO count in the RDEVBLOK and start the device if it is available. If not (device
busy or already scheduled) queue the IOBLOK and return the operation
to the caller. Entered via SVC. Entry point indicates virtual machine initiated I/O event. Preserve VMBLOK address in Rll, turn off IOBCP bit in the IOBLOK, add 1 to SIO count in the VDEVBLOK (or RDEVBLOK). Process
the SIO if there is any available path to the device. If not, queue
the IOBLOK and return the operation to the caller. STANDARD DASD I/O INITIATED VIA DIAGNOSE DMKDGDDK ---perform si.ple disk I/O of a standard format. Entry is via DMKHVC code X'18'. DMKSCNVU ---rInd-device related to SIO cuu address. DMKFREE -- Allocate storage for IOBLOK and RCWTASK. DMKGDDK ---SuIld and check the CCW string. Execute I/O. On completion, post condition code (and error return
code in R15, if detected). DMKDSPCH dispatcher. 1-190 IBM 1M/370 System Logic and Problem Deter.ination--Voluae 1
GENERAL I/O OPERATION INITIATED VIA DIAGNOSE DMKGIOEX ---Perform general I/O operation. Entry is via DMKHVC code 20. DMKSCNVU ---Pind-device related to SIO cuu address. DMKFREE Allocate storage for the IOBLOK. DMKCCWTR ----Buila the read CCW list. Queue the I/O request for execution. DMKGIO, DIAGRTN ---On-interruption return, check status. If no proDiem encountered, free storage used for ccw string and IOBLOK. DMKGIO, DIAGRTN ---aeflect-the-condition code and return code to the user. DMKDSPCH dispatcher. DMKUNTRN ---on-returned error condition, convert real CSi to virtual CSi and set
in user's page O. DMKGIO, Exit via SVC 12. VIRTUAL MACHINE I/O INSTRUCTION SIMULATION AND INTERRUPTION REFLECTION DMKVSIEX -- Entry from DMKPRV to simulate I/O per VMBLOK's VMINST field. On detected SIO, call - DMKSCNVU ---ro-Iocate VCHBLOK, VCUBLOK, and VDEVBLOK for the cuu called per SIO instructione DMKVSIEX ---netermine device availability and set condition code accordingly. If the operation is warranted, schedule the operation. For TIO, check device status, pending interrupts, and set appropriate
condition codes. VIO.!!!Q For BIO, check for dedicated channel, CE, CU, or device busy
condition, and subchannel busy and set appropriate condition codes. Check for dedicated selector or busy channel and check for pending
abnor.al interruption and set appropriate condition code. CP Method of Operation and program Organization 1-191
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