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I am trying to get my head around UEFI (Unified Extensible Firmware Interface) and it's not entirely clear to me how this affects virtual machines.

Thus, there are three parts to this question:

  1. Is UEFI an advance in hardware support for virtualization?
  2. All other things being equal, would a machine with UEFI be more likely to run a virtual machine more efficiently than one without, or does UEFI cause any performance hits that negate any speed improvements from a virtual machine?
  3. Would the difference in execution be visible to code running in a virtual machine? (In theory, it shouldn't, but in practice?)
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migrated from stackoverflow.com Nov 12 '11 at 14:56

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2 Answers 2

up vote 5 down vote accepted

UEFI shouldn't add any efficiencies all by itself, since BIOS and UEFI are there to bootstrap a system from bare CPU to an OS, and provide a translation layer between the OS and the hardware once things are booted. UEFI has a lot more capabilities in this regard.

It is entirely possible that VMWare (and the other VM vendors) will develop a hypervisor that runs directly from UEFI. Right now, it launches the hypervisor the same way it would a normal OS. Would running directly in UEFI be more efficient? Possibly, though probably not by much.

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Thanks! I guessed this might be the case, but I think you've hit on the critical issue: "Right now, it launches the hypervisor the same way it would a normal OS." So, changing the hardware won't do as much as what may come from VMWare and others to take advantage of these capabilities. That's good news: I can focus on what the VM vendors offer. –  Iterator Nov 12 '11 at 16:01
    
The only thing left is that we hopefully soonifh start seeing an UEFY option in Hyper-V and VmWare - basically boot into UEFI and not a bios ;) –  TomTom Dec 6 '11 at 13:08

If you want to see how UEFI firmware supports Virtual Machines, there is a project in the open source UEFI reference implementation EDK II: The Open Virtual Machine Firmware (OVMF). contains a sample UEFI firmware for QEMU and KVM.

http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=OVMF

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The whole project looks interesting. Thanks! –  Iterator Dec 7 '11 at 17:23

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