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RE: [Xen-devel] Configuration of nestedhvm

To: Keir Fraser <keir@xxxxxxx>
Subject: RE: [Xen-devel] Configuration of nestedhvm
From: "Dong, Eddie" <eddie.dong@xxxxxxxxx>
Date: Fri, 8 Oct 2010 15:56:56 +0800
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Thread-topic: [Xen-devel] Configuration of nestedhvm
Keir Fraser wrote:
> On 08/10/2010 05:34, "Dong, Eddie" <eddie.dong@xxxxxxxxx> wrote:
>> Nested virtualization usage model is emerging, however we must
>> guarantee it won't impact the performance of simple virtualization.
>> This patch add an boot parameter for nested virtualization, which is
>> disabled by default for now.
> What's the point when a per-domain config option is going to be
> implemented? You can then simply not configure nestedhvm for a domain
> you want to test without that capability? I suppose it makes your
> second patch make a bit more sense than it would in total isolation.

I want double-lock (AND) like other components such as IOMMU. 
If the global switch is off, even per domain configuration is turned on, the 
final effect is "OFF". 

The point here is to avoid manual mistake when the nested code is built in as 
formal release but targeting for pilot. Relying on HVM guest configuration only 
may cause the host crash or performance impact if the code has a bug and a 
guest enables nested virtualization feature.  

This switch is mainly for developer only at least for now.

> I think patch#2 probably makes sense, but it should wait for the
> patch that actually implements the per-domain config option, and
> properly implements is_nestedhvm(), before going in.

Yes, I am waiting for the take of that patch from Chris as well, but for some 
reason it is not in yet :(

Either patch is taken first is fine. I can do the simple rebase.

>  -- Keir

Thx, Eddie

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