Talk:Full virtualization

VirtualBox is not an example of Full Virtualization. It is a type two OS level VM.

Virtualization method is different and apart form Simulation or Emulation methods. Emulation is replication, Simulation is modelling while Virtualization is creation of another environment. Each method is separate and apart form others. The word Virtualization was not part of computer science, IBM, Microsoft or Intel Vocabulary prior to 2002. See Microsoft Computer Dictionary, Fifth Edition, 2002, ISBN 0-7356-1495-4.

History of Virtualization

in the late 90's three companies set out to solve the multiple OS-environments support issues on the X/86 platform. At that time. Microsoft Operating systems dominated desktops and server platforms with over 98% market-share. These companies included TransMeta, VMWare and Flash VOS. Each of these companies were awarded patents for their respective contributions to advancing their underlying technologies and methods.

Transmeta followed a purely hardware/firmware solution to "morph" various platforms using Simulation method. VMWare followed a purely software solution to support Virtual Machines to the IBM's late 60's and early 70's technologies by using Emulation methods and binary rewriting. Flash Vos followed a systems approach requiring improvements to all aspects of Hardware, Firmware and system software in cooperation with Compaq and Intel. The Flash VOS patents globally in the U.S. and China ushered in the true virtualziation methods and what is now termed Type-1 Virtualization. VMWare followed this lead and called its method Partial Virtualization (or Paravirtulization).

Flash VOS is primarily credited for innovations including OS-Independent Storage Management (Storage Virtualization), Super OS/Hypervisor operating at a higher privilege level than OS or Programs (Kernel/User modes) also called virtualizing Kernel, Fast Switching of platform to support multiple virtual environments and Packing of instances for relocation which is the basis of Elastic Computing. See U.S. patents US6401183, US6690400, US07356677 among others.

Microsoft was threatened by Flash VOS and strictly forbid its support by its resellers that included HP, DELL, Compaq, Sony among others. Micorsoft was not amused by Flash VOS's motto and advertising headline trumpeting "Opening the gates of development by closing Gate's development". However, the influence of Flash Vos technology endured and is apparent in adoption of Flash Vos privilege rings by Intel.

VMWare enjoyed the most commercial success by supporting Microsoft strategy and emulating Linux environments under Windows as the first commercial product. This best fit dominant players business plan. The open source community development of Partial Virtualization products such as XEN also gained acceptance. However, after 2006 and introduction of Intel VT-x technology type-1 virtualization got a new life. Today, Type-1 virtualization is the dominant choice of cloud service providers. OpenStack provides a most complete suite of virtualization system software which supports virtually all Hypervisors including KVM, XEN, LXC, Hyper-V, etc.

Virtualization owes most not all of its success today to pioneering innovations of Flash Vos. Giving this credit to IBM for 360/370 emulation solutions or Virtual Machine innovations of late 60's is inaccurate at best.

This topic is referenced in a few places, and so it clearly needs an article. It is not quite clear (to me) that this term is universally understood or used as such; this page is thus probably more of a sub-article to virtualization than a legitimate stand-alone term. However it is used in enough places that at least it needs a link target!

This description is also somewhat CP/CMS centric (for obvious reasons). Other examples of full virtualization would be a good addition. It could probably use some rewording and clarifying as well but I thought I needed to get something out here so the links would turn blue. Trevor Hanson 02:19, 5 December 2006 (UTC)

this entry is vmware specific without mentioning i.e. xen technology and thus does not offer an impartial view on the subject, needs enhancement and some links to other recent technologies 87.187.179.183 (talk) 11:40, 2 June 2008 (UTC)

After reading the definition of "full virtualization" in this article, it seems to be what usually is meant by strict/complete/instrinsic compatibility of a VM (according to Smith/Nair's "Virtual Machines"): every behaviour of a real system has to be emulated exactly, such that there is no way for a guest to detect that it is running in a VM. Another term is "complete transparency". These terms definitely should be mentioned here.

Further, "Similarly, full virtualization was not quite possible with the x86 platform ..." makes no sense. Any kind of virtualization can be implemented in software. If it's getting slow, correct the emulation of time for the guest. Joe0815 (talk) 19:04, 2 July 2012 (UTC)

The thing is that despite this being sourced almost entirely from VMware's taxonomy document (which isn't without some traction in literature), the examples are actually incorrect, as full virtualization doesn't require hardware assist according to VMware. Also, you can detect VMware and any current x86 hardware supervisor without much difficulty. There's no such thing as complete transparency. It might be more so on IBM's mainframes, but I don't know enough to comment on that. Someone not using his real name (talk) 11:48, 18 February 2014 (UTC)

Usage of the Term "Reflected"

It would seem that the term "reflected" as it appears in the following sentence,
"Full virtualization requires that every salient feature of the hardware be reflected into one of several virtual machines – including the full instruction set, input/output operations, interrupts, memory access, and whatever other elements are used by the software that runs on the bare machine, and that is intended to run in a virtual machine.",
is incorrect, or at least confusing. "Reflected" is not used in that sentence in a way consistent with its other usages in Wikipedia, or with its definition as stated in Wikipedia. Perhaps a better term would be "realized", "emulated" or "re-presented"? (Erenoh (talk) 15:24, 28 December 2012 (UTC))

Anyway, it is the term used by IBM in regards to the VM operating system. I/O for example: The hypervisor intercepts the SIO (Start I/O) instruction, and translates the virtual memory and device addresses (real addresses to the operating system of the virtual machice) to real ones, and performs the actual I/O operation. When the operation is completed, the control unit signals that to the hypervisor by an interrupt. The hypervisor translates the real addresses of the interruption data to virtual ones (again real ones to the operating system of the virtual machine), and reflects the interrupt to the virtual machine by simulating the behavior of the hardware: Stores the current virtual PSW from a known virtual location and loads a new virtual PSW from another known virtual location, thus forcing the virtual operating system to enter the first-level interruption handler code. All virtual interrupts are not caused by real interrupts. For example the CP DIAL command (connect a new virtual terminal to a virtual machine) causes a virtual power-on interrupt to be reflected to the operating system as a notification. Thus, the operating system can react exactly in the same way it would react if running on a real hardware. --Gronroos (talk) 14:56, 22 March 2018 (UTC)

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