Re: [Xen-devel] Re: VT-X processors , xen 3.0 , drives and virtualization (in 32 bit environment)

[Ian Brown <ianbrn@xxxxxxxxx>]

Hello,
  Ok, Thnks,this clears a lot about the first question.

Still, I will be grateful if I get any feedback on the second question
: performance overhead of running more than one Linux OS instance on
these VT-processors :
did anybody tried it and can comment on it / give some data / compare to
non VT processors
(which have aboutb 3% performance overhead) ? I would expect that
somebody had tried using these
VT chips (even they are still (maybe) in beta stage ).

Regards,
IB


On 12/27/05, Charles Duffy <cduffy@xxxxxxxxxxx> wrote:
> Ian Brown wrote:
> >  1) True to now and the current xen-3.0 version: When running Xen 3.0
> >  on these VT processors, can we run an unmodified kernel ?
>
> For your DomUs, yes. For your Dom0, no. Running a modified DomU kernel
> should be more performant.
>
> >  and in such a case, what about the device drivers - isn't there a
> >  problem with them ?
>
> Emulated hardware, based off of drivers borrowed from QEMU, is provided
> to VMX domains. The drivers they need will be for the emulated cards,
> not for the real devices in the machine.
>
> > I mean , in practical terms , if I will set my bootloader to have the
> > following entry on a machine with VT-x processor:
> >  kernel /xen.gz dom0_mem=x
> >  module /vmlinuz-#version ro root=...
> >  (and initrd if needed)
>
> No, that won't work, because that's trying to use an unmodified kernel
> as Dom0.
>
> > will I be
> > able to create a new domain based also on unmodified vmlinuz-#version
> > kernel ?
>
> Yes, though VMX domains work a bit differently from non-VMX ones -- the
> process won't be exactly the same except with a non-Xen-enabled kernel.
>
>
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