Re: [Xen-users] Xen: The processor(s) in this machine do not support full virtualization.

["Javier Guerra" <javier@xxxxxxxxxxx>]

On Wed, May 21, 2008 at 9:35 AM, "Jörg Kühne" <joerg.kuehne@xxxxxxx> wrote:
> Hello,
>
> did that mean my local processor doesn't scope the perfomance which is needed 
> for virtualization?

it's not a matter of performance, it's about processor features.

traditionally, the x86 architecture supported a limited kind of
virtualization, meant to be used by OSs to isolate different tasks on
the same OS; but not to isolate several OSs running at the same time.

without that, several software  packages managed (qemu/kqemu, VPC,
VMWare) to do VM by a complex combination of emulation and
virtualization.  it's really hard to do given the chip limiatations,
and even harder to do it efficiently.

Xen's original idea was to do Paravirtualization (PV), that means
modifying the 'guest' OS so that it doesn't need to be _totally_
virtualized.  it runs really well, and gives great performance, but
can't be done if you don't have the source code (and license) to
modify the OSs.  that means it works for Linux, BSD (and a few others)
guests; but not windows.

both Intel and AMD decided to add hardware to their chips to help with
that, (several names, lets settle on HVM).  with HVM chips (Pentium M
wasn't one of them), Xen can (with some help from qemu) create a
'fully virtualized' guest, able to run windows (and more 'unmodified'
OSs).  it's slower than PV, thought.

so, what that message means is that you can run PV guests, but not HVM
ones.  IOW: windows is out, linux is in.

hope that helps

-- 
Javier

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