what's the difference between vbox-kmod and kvm?

[fpemud]

kvm is composed by 3 kernel module: kvm, kvm_intel, kvm_amd
vbox also has 3 kmod: vboxdrv, vboxnetadp, vboxnetflt

What's the difference between them in function, technical rationale and interface?
And why vbox or vmware can't use kvm directly?

As far as I know, all the virtual machine products require same kernel function.
So I think vbox should use kvm for the basic function, plus its own kmod for addtional function.

I have found some kvm doc, but can't find andy doc for vbox kmod.

[salahx]

The kvm modules are a relatively thin layer to the hardware virtualization features. Note that kvm is not in and of itself a virtualization solution, just the kernel interface, it needs user-space host, like qemu .

The vboxdrv modules is to Virtualbox what the kvm module is to qemu. It also have several ancillary modules for networking: vboxnetadp and vboxnetflt. In theory, virtualbox COULD use KVM instead of it own module, but it doesn't (doubt it'll ever happen, but would be nice, as vboxdrv inspired a new taint flag: TAINT_OOT_MODULE)

Virtualbox is oriented toward virtualizing desktop environment as opposed to servers - but qemu/kvm has come a long way with things liek virtio, spice, and libvirt. However qemu/kvm/spice does not (yet) support host accelerated video, while VirtualBox does.

[fpemud]

thanks for your reply.

Another question about the orientation:
I guess it is more of feature development priority, not about the design?
I hope there's nothing like "qemu's design is for server only, not appropriate for desktop, VirtualBox is specially designed for desktop usage".

[salahx]

There no inherent reason why virtualbox can't be used for server usage, or qemu/kvm for desktop usage. Virtualbox is developed more of a "turn-key" solution to desktop virtualization, whereas qemu is more piecewise: qemu handles instruction and hardware emulation; kvm handles the virtualization acceleration; libvirt the configuration, management and user interface; virtio provides efficient guest/host I/O; and spice the video, input and host integration.

When virtualbox was intially release, qemu-kvm was just a fork of qemu, spice didn't exist, virtio was in its infancy and libvirt was still very young.