On Fri, 05 Oct 2007 09:09:22 EDT, der Mouse said: > Software cannot tell when it's running under emulation, if the > emulation is sufficiently good; this just means that VMware is not > "sufficiently good" for those purposes. There must be something > they're not emulating correctly (where "correctly" here means "the way > real hardware does it").
Right. The problem is that some pieces are really hard to emulate well enough. > Perhaps someone should approach the VMware people about producing a > version that *is* "sufficiently good"? There may be hardware issues that prevent it. You basically have 2 ways you can do a virtual machine: 1) Software emulate each opcode, which allows (at least in theory) a 100% chance of doing a perfect emulation, but which comes with some nasty performance hits. 2) Let the software run natively, but in a box that traps all traps and privileged opcodes and emulates those. This allows it to run at near-hardware speed, but has a hardware-dependent issue: You're screwed if there's a non-privileged opcode that will reveal which ring or privilege level you're running in (as you need to be in a lower-priv ring than expected in order to cause the traps and interrupts that drive the emulation). The 32-bit x86 architecture is *known* to not be fully virtualizable, as are earlier 64-bit from both AMD and Intel. So basically, if you're on an x86 chipset that doesn't have the VM extensions, you're *known* to be screwed, and the jury is still out on whether the VM extensions are sufficient, or if there's still errata and loopholes.
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