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RedBend: There’s nothing “optional” about virtual machine isolation


A week or two ago “mobile virtualization” provider RedBend created a bit of press announcing their vLogix Mobile 5.0, which they claim is much faster to integrate than other solutions. (If you look at what architectures are supported, you know why: they target only ARM Cotex-A15 and Cortex-A7 cores, which are the ones with hardware virtualization support. Sure if you don’t para-virtualize things go faster. Have a look at our evaluation of ARM’s hardware support for virtualization with the first hypervisor that supports it).

So far, so boring. They also make claims that their mobile virtualization solution is deployed more widely than all the others concerned, a somewhat amusing statement, given that to date not a single product has been publicly identified that uses RedBend virtualization! If so many use it, why don’t they own up?

What most surprised me when looking at their web site is that they still have an optional isolator module. Does this sound familiar? Well, that’s exactly what VirtuaLogix (which RedBend bought in Sep’10) had! I had examined this in detail 4 years ago and pointed out that isolation of virtual machines is an inherent consequence of virtualization, not an optional add-on. What was behind is that VirtualLogix used a pseudo-virtualization approach which runs guest OSes in privileged mode, at the same privilege level as the hypervisor. Their optional “isolation mode” meant de-privileging the guest, exactly what the rest of the world calls “virtualization”.

I find this all a bit dishonest. In fact, if we were talking about a consumer product sold in Australia, I would ask the Dept of Fair Trading whether this might constitute misleading advertising…

Also, I would have thought that they would have learned how to do it properly in the meantime. Reading the description of the “optional isolator” on RedBend’s web site, it seems not.

I can only repeat my old recommendation: Take a good OS course, guys! Such as the Advanced Operating Systems course I teach at UNSW. There you’ll not only learn the concepts, you’ll also learn how to design and implement kernels so they perform without shortcuts.

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