Robert McLaws: Windows Edition

Blogging about Windows since before Vista became a bad word

Clearing the Air About Vista and Virtualization

The Associated Press paraphrased Microsoft's Scott Woodgate as saying "Microsoft considered banning virtualizing Vista entirely, on all versions." Some people have been characterizing it as saying that Microsoft wanted to "remove virtualization from Vista."

There's only one problem with that line of thinking. You can't "remove virtualization" from the operating system. With the exception of Xen and Viridian, virtualization is a function of add-on software that sits on top of an operating system, not inside it. Virtualization is enabled through emulating a hardware platform through software. Some virtualization platforms add special drivers that can give virtual hardware access to physical hardware. But with Microsoft's current technology, the hardware emulation platform cannot run on "bare iron", or Ring 0 of the kernel.

Now, with Xen and Viridian, all that changes. That's because both sit between the hardware and the kernel, in a place some people call "Ring -1." Every installation on top of Viridian is a virtual one, even the primary operating system.

Having said that, Vista is aware of when it's running in a virtualized environment, and can make optimizations when it does so. Conversely, they could have put in technological barriers that would prevent Vista from running in a virtualized environment, but they haven't even done that. The only virtualization limitation in Vista Home Basic or Home Premium is a legal one.  (That's not to say it's not important, I'm just saying that MS didn't go to extreme lengths to enforce the EULA, nor am I advocating that anyone break their EULA). I know this for a fact, because I just installed Windows Vista Home Basic on my Windows Vista Ultimate machine, and it runs just fine. I'll be trying to install Virtual PC 2007 on Home Premium tomorrow evening to make sure It will work there too... I'll report the results then.

Besides that, why is the fact that they considered banning it in the EULA news? They didn't do it, so who cares? I've considered what my legs would look like if I replaced my feet with roller blades, it doesn't mean I've done it.

Anyway, just wanted to clear that up.



  • Toph said:

    BREAKING NEWS!!! Robert McLaws wants to replace his feet with roller blades!!

    February 25, 2007 10:35 PM
  • LMAO!

    February 26, 2007 1:29 AM
  • Massif said:

    What I really don't get about this whole debacle is that MS haven't banned virtualisation at all.

    Reading the EULA carefully makes it clear (albeit legalese-clear) that the only thing you're not allowed to do on versions other than ultimate is install Vista, install a VM and install the same copy of Vista inside that VM. On Ultimate you can do that as well though.

    What's the big deal? Nothing's been banned and in one case you're actually allowed to effectively use the same license more than once. Relax everyone.

    Surely wearing rollerblades would give you a pretty good idea of what your legs would look like with rollerblades instead of feet?

    February 26, 2007 9:21 AM
  • Don said:

    If you ignore the usual sensationalist headlines, there seemd to be two themes:

    1. Micrisoft had carefully considered concerns over "Vista is aware of when it's running in a virtualized environment, and can make optimizations when it does so" being a possible security weakness

    2. speculation on whether those optimizations were removed from the unsupported versions

    February 26, 2007 4:45 PM
  • Don said:

    I wonder if there is a way to (easily) test for the vitualization optimizations in guest vistas for all the versions of vista.

    That might also be an interesting test of how useful they are if there is a way to test with them both on and off...

    February 26, 2007 4:53 PM