Should VT-x Be Enabled If Not Being Used?

[BBach1]

Searching the web brings up quite a few answers to this question, but many of them are contradictory to one another, and I am hoping that someone from Intel can shed some REAL light on the question:

Put simply, if I am building a physical machine (workstation or server) and do not intend to use any manner of virtualization in the environment, should the VT-x extensions be enabled in the BIOS or not? More importantly -- explain your answer!

I understand that the extensions are needed if you will ever do a VM -- this makes sense. But is there a cost to enabling the extensions? Does any part of the CPU run more slowly? Less securely? Many posts on the general web say that it doesn't matter -- but if it really didn't matter, why would hardware/bios vendors expend time and effort to even make it an option?

[idata · Accepted solution]

Hello,

Here are the answers to your questions:

1- VT-x extensions must be enabled when working on a virtual environment only. The Operating System (host machine using ESXi 5.5 as an example) will use these extensions to install the Operating System successfully and ensure the functionality of the virtual machines. If you do not have a virtual environment you will be calling BIOS features which the Operating System will not take advantage of and that will increase the CPU usage for no reason.

1. The CPU will not run slower neither affect performance or security, is just the simple fact that you are enabling extensions that a regular Operating System will not use at all.

[BBach1]

Forgive me for being picky, but you state in the first paragraph that enabling VT-x without using virtualization will "increase CPU usage for no reason", and then you say in the second paragraph that it will have no impact on performance. If the CPU is busier, then surely performance will be impacted on a heavily-loaded system as those cycles are not available for use by other processes.

Again, why would BIOS developers include an on/off switch for this feature is turning it on has exactly NO ill effects of any kind?