Enabling hardware virtualisation BIOS; anything to beware?

A lot of recent virtualisation tools can either make use of, or demand, BIOS support (Intel-VT, AMD-V, etc). But in most of the BIOS screens I’ve seen, it has been disabled by default – sometimes even with fairly non-subtle (but vague) warnings.

So: is there any issue I should be aware of in enabling VT? I assume it is only used when triggered deliberately by software such as VMware or Virtual PC. But what is the risk?

Perhaps it relates mainly to the early implementations where it was a bit experimental, but I’d love to know: is it generally safe?

The Blue Pill was a proof of concept, that this could be potentially used by malware, making that malware completely invisible to the OS.

Check more discussion of this question.

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