Re: [Xen-devel] Testing nested virtualization on Intel CPUs

[AP <apxeng@xxxxxxxxx>]

On Sep 20, 2011 10:57 AM, "Tim Deegan" <tim@xxxxxxx> wrote:
>
> Hi,
>
> Cc'ing Eddie Dong, who wrote this code.
>
> At 18:16 -0700 on 16 Sep (1316196980), AP wrote:
> > I am testing out nested virtualization on a Lenovo x220 (Intel
> > i7-2620M). I am running xen-unstable (23842:483c5f8319ad) and Linux
> > 3.0 (Ubuntu 10.10).
> > I brought up a Centos 5.6 VM and installed Xen that is packaged with
> > it. I think it is a variant of 3.0. The CentOS Xen VM boots very
> > slowly but it does finally come up in to the nested Dom0.
>
> Yes, booting Xen as a nested guest is very slow at startup, because of
> how Xen relocates the bottom 1MB at boot time.  You might find that
> 32-bit Xen boots faster.
>

Could please expand a little on why the relocation causes it to slow down?

Thanks,
AP

> In general I expect performance of a nested-HVM guest on Intel to be
> quite poor, because it doesn't yet have nested EPT support.  Eddie, is
> that something you're working on?
>
> Tim.
>

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