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

To: AP <apxeng@xxxxxxxxx>, Eddie Dong <eddie.dong@xxxxxxxxx>
Subject: Re: [Xen-devel] Testing nested virtualization on Intel CPUs
From: Tim Deegan <tim@xxxxxxx>
Date: Tue, 20 Sep 2011 18:57:12 +0100
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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.

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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