Comment by veber-alex

3 years ago

KVM is a type-1 hypervisor [1]

[1]: https://www.redhat.com/en/topics/virtualization/what-is-KVM

There's arguments in both directions for something like kvm. Wiki states it pretty well:

> The distinction between these two types is not always clear. For instance, KVM and bhyve are kernel modules[6] that effectively convert the host operating system to a type-1 hypervisor.[7] At the same time, since Linux distributions and FreeBSD are still general-purpose operating systems, with applications competing with each other for VM resources, KVM and bhyve can also be categorized as type-2 hypervisors.[8]

https://en.wikipedia.org/wiki/Hypervisor#Classification

Not really, calling KVM a type-1 is a misunderstanding of what the “bare-metal” distinction is referring to. The real difference between the two types is whether the hypervisor owns the hardware or not. In the case of a type-1, the hypervisor runs below the kernel and controls access to the hardware, even for the kernel. In type-2, the hypervisor runs on the kernel, which owns the hardware, and must go through the kernel to use hardware resources.

  • But that's not how that works. KVM is as "bare-metal" in access to the system as ESXi is. The hypervisor code runs in ring 0 in both cases.