Just an intro.

Tony Baechler tony at baechler.net
Mon Mar 25 08:47:04 UTC 2013

No, it won't.  KVM and Qemu are two different packages, at least on Debian. 
  If you call qemu by itself, you don't use hardware virtualization.  If you 
call kvm without a kvm module loaded, it exits or falls back to Qemu. 
Perhaps this has changed with newer versions of Qemu, but every version of 
Qemu I've used is separate from KVM.  However, I think they merged the Qemu 
and KVM code, so you might be right nowadays.  There is a difference though 
and they aren't the same thing.  Even in Debian and Ubuntu, you install 
qemu-kvm, qemu-system and qemu-user if you want a full Qemu and KVM setup.

You might be thinking of the kernel Qemu module, but it is now abandoned and 
no longer recommended.  Debian no longer ships it, so it's either straight 
Qemu without virtualization or KVM if your CPU supports it.  Not all 
hardware supports virtualization, even now.  ARM processors wouldn't, for 
example.  My CPU here on my desktop isn't that old and it doesn't, thus 
bringing me back to why I don't run Windows in a VM.  Even with KVM, there 
is a slight performance hit, but not much.

On 3/24/2013 12:23 PM, Christopher Chaltain wrote:
> Just a note that qemu will use kvm if hardware virtualization is available,
> so you won't get that performance hit with qemu in those cases.

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