Introduction to virtual machines (V)-IBM Virtual Machine Model

IBM Virtual Machine Model

InIBMIn the model, each virtual machine is a complete copy of the real machine, but the memory is a little less.

IBM (International Business Machines) virtual Machines are currently one of the mainstream virtual Machines in use. In the IBM model, each virtual machine is a complete copy of a real machine, but the memory is a little less. According to this concept, a powerful large host can be divided into many virtual machines. These virtual machines only have less resources than the original host.

The IBM virtual machine version is similar to other virtual machine genres because it also provides function ing services. This means that virtual machines are responsible for interpreting virtual commands and ing them into actual machine commands. For IBM virtual machines, the ing of such commands is basically a one-to-one ing. This means that a virtual instruction only corresponds to an actual instruction and completes the work of an actual instruction. In essence, users are actually accessing and executing machine commands.

Now, you may be confused: If the ibm vm operating system actually gives all the functions of the actual machine to the user, how can it ensure security? Security is also achieved through ing. You only need to block or restrict a specific instruction set that is considered sensitive, such as instructions that attempt to access the processor memory (registers. If you allow access to such commands, you are allowed to directly modify the actual machine and change other running virtual machines. If this happens, the virtual machines of each user are not completely irrelevant and may damage the environment of other users.

In essence, the ibm vm system directly executes all non-sensitive commands and intercepts sensitive commands. After the machine intercepts these sensitive commands, it will try to simulate the expected operation so that users will not notice that they are trying to perform an illegal operation. If possible, the VM system provides a virtual execution for sensitive commands to provide users with all the functions they want while maintaining the system integrity of the OS/370 hardware. All these functions are provided by virtual operating systems running on hardware.

How does it work?

 

Therefore,IBMThe virtual machine system not only allows sharing resources, but also protects system resources.

The virtual machine operating system is the "brain" of the entire IBM virtual machine architecture ". The entire System, including the operating System and hardware, is called a virtual machine System ). Every virtual machine system is controlled by a program called a control program. In addition to managing physical hardware, the control program also creates a virtual machine for each system user, which is a full simulation of 370 systems or 390 systems. The focus of the IBM virtual machine concept is that every user can run programs, store data, or even crash the Virtual Machine on their virtual machines, without affecting the virtual machine system itself and other system users. Therefore, the IBM virtual machine model not only allows resource sharing, but also protects system resources.

In fact, the control program runs directly on the host hardware, which is the most important part of the Virtual Machine System. The control program must manage system hardware, including system support tasks including startup and shutdown, and request queuing and execution. At the same time, the control program also manages the programming features of each virtual machine and the establishment and maintenance of each virtual machine.

In addition to the control program, another important component for user interaction with virtual machine systems is the Conversational Monitor System (CMS ). This title sounds complicated, but CMS only provides the basic tasks of the operating system that the user needs. These include file system commands, program loading and execution functions, memory management, screen and window services, and services that allow users to write applications. CMS is an operating system for a single user and a single task. Although the system has the ability to process multiple tasks at the same time, it was initially used as a single task system. Each virtual machine has its own CMS copy, so that all users have the same interface and functions.

IBMThe instruction sets of virtual machine systems are actually one-to-one correspondence.

In addition to CMS, the VM System also has some other components, including the Group Control System and Transparent System Access Facility ), some additional services and Dump Viewing Facility ). I know that you may be wondering what the official terms mean. To be honest, the things mentioned above are not important for a general understanding of IBM virtual machine systems. Therefore, we will focus on how control programs and session monitoring systems map commands.

As mentioned in the summary, the instruction sets are actually one-to-one ing. Based on speed and convenience, most of the commands on the 370 and 390 systems are directly run by the system. This means that CMS allows users to run commands without any speed loss and obtain the desired functions. What I want to talk about most is a small subset of commands. The VM system regards this subset as sensitive.

A sensitive Command actually refers to a command that allows the user to change the status of another user's virtual machine, the hardware status of the system, and other sensitive or protected functions. To illustrate this problem, let's look at an example:

For example, a user tries to execute a command that can access other users' virtual machines and resources. This command will beInterception, AndMarkIs a sensitive command. This means that CMS will treat this directive as a protected directive, and then add a special flag when it is passed to the control program, which will tell the control program: "This is a protected command." Computer terminologies are called interruptions, but this is not important to this article.

The Control Program receives a flag command that tells the control program that it is a sensitive command. Then the control program executes some specific routines or checks on this instruction to decide how to handle it. These routines can tell the control program whether to simulate the execution of this command, or whether to completely stop the execution of this command. If the control program simulates this command, the user will never know that they are trying to execute a sensitive command, and their system will continue to execute as nothing special happens. If the control program must stop the execution of this command, it will return a message to the user to tell them that an error has occurred. User Programs may stop execution.

Summary

After reading the above sections, you now have a basic understanding of what IBM Virtual Machine Models and How IBM virtual machines work. This is good, but I bet you are sure that this model can really work? Does it really work as advertised? I have used this system. To be honest, it does work.

The IBM virtual machine system providesSecurityIn this environment, multiple users can share large systems.

The IBM virtual machine system providesSecurityMulti-User Sharing of large systems in the environment. By creating a copy of a real machine for each user, the IBM system allows each user to obtain the same functions and resources without compromising the encapsulation and security of any user. After nearly thirty years of development, the system has been stable enough. This makes it a resource sharing system widely used in enterprises and universities.