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Is KVM a type 1 or a type 2 hypervisor?

I understand that type 1 hypervisors run on bare metal while type 2 hypervisors are applications running on top of an operating system (such as VMware Workstation). I also understand that the performance difference between type 1 and type 2 clients can be significant.

I am confused as if KVM is type 1 or 2 as I understand that a desktop environment can be installed in dom0.

Pétur Ingi Egilsson
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    sad to see this marked as off-topic. This is quite focused Q and is on-topic and worth discussion !! – samshers Sep 13 '20 at 11:31

2 Answers2

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KVM is not a clear case as it could be categorized as either one. The KVM kernel module turns Linux kernel into a type 1 bare-metal hypervisor, while the overall system could be categorized to type 2 because the host OS is still fully functional and the other VM's are standard Linux processes from its perspective.

The desktop environment i.e. GUI has less to do with this. It's more clear if we compare this to Hyper-V, where the hypervisor is a distinct layer beneath all the virtual machines: even dom0 is technically just one VM among others, despite it has special privileges and it is the one shown in the console, having a GUI. Therefore, if we stare too much at the appearance, Hyper-V might look like type 2 while it is purely type 1.

Esa Jokinen
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If Hyper-V is type 1, then KVM is type 1 as well. There are no hardware services being emulated by the operating system in KVM. Frankly, the whole type 1 vs type 2 terminology is obsolete and should be retired, since nearly all modern hypervisors rely on hardware-assisted virtualization and guests run at speeds approaching that of bare metal.

Art Cancro
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