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Browse Prior Art Database

Multi-Scp Device Isolation

IP.com Disclosure Number: IPCOM000041358D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fleury, SL: AUTHOR [+5]

Abstract

When executing preferred guest virtual machines (such as virtual machines using the IBM MVS/370 or MVS/XA system control program (SCP)) on a hypervisor (like the VM/370 SCP) operation on a CPU using the S/370XA architecture, it is essential to keep the hypervisor overhead to a minimum. One area of overhead to attempt to eliminate is having the hypervisor receive interrupts which are for the performance oriented guest machine, e.g., a preferred guest. In uniprocessor (UP) environments, there is little that can be done, since the I/O new PSW can only cause execution on one CPU. However, in multiprocessor (MP) environments, two (or more) interrupt handlers can be provided to operate under different priority interrupt classes in the S/370XA architecture. The I/O devices in the MP are divided into sets.

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Multi-Scp Device Isolation

When executing preferred guest virtual machines (such as virtual machines using the IBM MVS/370 or MVS/XA system control program (SCP)) on a hypervisor (like the VM/370 SCP) operation on a CPU using the S/370XA architecture, it is essential to keep the hypervisor overhead to a minimum. One area of overhead to attempt to eliminate is having the hypervisor receive interrupts which are for the performance oriented guest machine, e.g., a preferred guest. In uniprocessor (UP) environments, there is little that can be done, since the I/O new PSW can only cause execution on one CPU. However, in multiprocessor (MP) environments, two (or more) interrupt handlers can be provided to operate under different priority interrupt classes in the S/370XA architecture. The I/O devices in the MP are divided into sets. Each set is then assigned to a single interrupt class among the plurality of priority I/O interrupt classes in the S/370XA architecture, which provides up to eight interrupt classes (or sets) and the sets of devices must be associated with different interrupt classes. The preferred guest is made to believe not all interrupt classes are useable by assigning its devices to a subset of classes and making out (by control register 6) its non-useable classes. This will allow all interrupts from devices in the sets dedicated to the preferred guest to be directed by the SCP dispatching program to a CPU which is dedicated to that guest. The converse i...