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I am considering moving several of my virtual machines to a single Linux system for a variety of reasons. The problem is that most VMs are KVM-based, but there are a few VirtualBox VMs as well.

I have found several posts (1, 2, 3, 4) that seem to boil down to this: It is not possible to use VirtualBox when the KVM modules are loaded. Therefore it is not possible to have both VirtualBox and KVM VMs active on the same host.

Considering that virtualization on Linux is developing at a fast pace, is this still the definitive word on this issue? Are there any workarounds? If not, is the ability to run multiple hypervisors somewhere in the roadmap?

PS1: I do not consider rmmod kvm to be a real workaround...

PS2: ...nor using either QEMU/KVM or VirtualBox in software emulation mode.

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up vote 6 down vote accepted

I doubt this will ever be possible, and it doesn't make any sense to have two virtualization systems compete over resources and control of the VT-X extension.

Even if this would work, I guess performance would be terrible.

Edit: It appears I am wrong and this is indeed possible at least in some cases. As this is a site for professional system administration, this is NOT a recommended mode of operation.

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I suppose that on production systems your reasoning is valid - one hypervisor per physical system should be enough. My case is somewhat of a corner case. I ended up moving the server VMs only by migrating them to KVM, although in some cases I had to reinstall the VM when the OS-that-shall-not-be-mentioned did not like the different hardware. I left the desktop VMs alone for the time being... – thkala Dec 14 '11 at 17:08
It might be possible, but you'd have to be either insane or extremely desperate to even think about doing it. I certainly would not take the risks this sort of Franken-setup would impose. – Michael Hampton Jan 12 at 14:30

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