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Virtualization doesn’t require VT-x or VT-d, those are just performance enhancement mechanisms for virtualization on 80386-derived CPUs. Most other 32-bit and 6
by eschaton 8y ago
Virtualization doesn’t require VT-x or VT-d, those are just performance enhancement mechanisms for virtualization on 80386-derived CPUs. Most other 32-bit and 64-bit CPU architectures have supported virtualization reasonably well from the start. The biggest popularizer of the technique was the IBM System/360.
For a microprocessor example, the Motorola 68000 almost supported virtualization, and the 68010 corrected the one flaw—insufficient exception context to restart an instruction—that prevented it. That’s why even though the personal computer market didn’t touch it, workstations migrated to 68010 as soon as it was available.
Of course there are a variety of ways to make virtualization easier on the implementer and more efficient to use. Intel’s enhancements really shine there. But they’re not required, just useful.
- m_mueller 8y agowould you agree that emulation can be put as a subset of virtualization, as the terms are used today?
- jki275 8y agoEmulation and virtualization are two very different concepts. Every OS you virtualize must be supported by the base processor in the hardware. That is not so in an emulation, where another architecture can be supported. See the differences between qemu and virtualbox.
- m_mueller 8y agoThis is in contradiction to eschaton, and I agree with GP in this regard: pass-thru of CPU instructions to host hardware is just an optimization, not a defining feature of virtualization. There were VM hosts before processors supported this, and back then I think that virtualization == emulation.