DomU as Dom0?

DomU as Dom0?

[Sassy Natan]

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Hi,


Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0 for
other DomU on top of it?



Thanks

Sassy

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Re: [Xen-devel] DomU as Dom0?

[Konrad Rzeszutek Wilk]

On Thu, Feb 11, 2010 at 09:43:59PM +0200, Sassy Natan wrote:
> Hi,
> 
> 
> Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0 for
> other DomU on top of it?

Can't do with Xen.

Re: DomU as Dom0?

[Daniel Stodden]

On Thu, 2010-02-11 at 14:43 -0500, Sassy Natan wrote:
> Hi,
> 
> 
> 
> 
> Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0
> for other DomU on top of it?

Domains don't stack. There's no concept of one domain running on top of
a different one, not even with the original dom0.

But many of the tasks dom0 performs on behalf of domU's could be done by
other domUs as well. Primary example would be I/O virtualization for
normal, non-privileged guests.

So the dependency graph you can build for a 'service' model is *much*
more flexible than the rather static 3-level block scheme depicting the
bare binary interface.

That's maybe not the answer you were looking for.

If you're rather looking for recursive virtualization, I don't think
that's going to fly all that well either.

Daniel

Re: [Xen-devel] DomU as Dom0?

[Sassy Natan]

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OK,

Thanks for the answers

Sassy

On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
<daniel.stodden@citrix.com>wrote:

> On Thu, 2010-02-11 at 14:43 -0500, Sassy Natan wrote:
> > Hi,
> >
> >
> >
> >
> > Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0
> > for other DomU on top of it?
>
> Domains don't stack. There's no concept of one domain running on top of
> a different one, not even with the original dom0.
>
> But many of the tasks dom0 performs on behalf of domU's could be done by
> other domUs as well. Primary example would be I/O virtualization for
> normal, non-privileged guests.
>
> So the dependency graph you can build for a 'service' model is *much*
> more flexible than the rather static 3-level block scheme depicting the
> bare binary interface.
>
> That's maybe not the answer you were looking for.
>
> If you're rather looking for recursive virtualization, I don't think
> that's going to fly all that well either.
>
> Daniel
>
>

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Re: DomU as Dom0?

[Thomas Goirand]

Sassy Natan wrote:
> OK,
> 
> Thanks for the answers
> 
> Sassy
> 
> On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
> <daniel.stodden@citrix.com <mailto:daniel.stodden@citrix.com>> wrote:
>     If you're rather looking for recursive virtualization, I don't think
>     that's going to fly all that well either.
> 
>     Daniel


It's called "nested virtualization" (not recursive) and there was a talk
about it on the last Xen Summit in Shanghai. I suggest you to read the
video:

http://www.xen.org/files/xensummit_intel09/xensummit-nested-virt.pdf
http://www.xen.org/media/Movies/XenSummitAsia09/2009-11-19-afternoon/NestedVirtualization.MTS

Thomas

Re: [Xen-devel] DomU as Dom0?

[Pasi Kärkkäinen]

On Fri, Feb 12, 2010 at 03:46:34PM +0800, Thomas Goirand wrote:
> Sassy Natan wrote:
> > OK,
> > 
> > Thanks for the answers
> > 
> > Sassy
> > 
> > On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
> > <daniel.stodden@citrix.com <mailto:daniel.stodden@citrix.com>> wrote:
> >     If you're rather looking for recursive virtualization, I don't think
> >     that's going to fly all that well either.
> > 
> >     Daniel
> 
> 
> It's called "nested virtualization" (not recursive) and there was a talk
> about it on the last Xen Summit in Shanghai. I suggest you to read the
> video:
> 
> http://www.xen.org/files/xensummit_intel09/xensummit-nested-virt.pdf
> http://www.xen.org/media/Movies/XenSummitAsia09/2009-11-19-afternoon/NestedVirtualization.MTS
> 

These videos are also available on youtube:
http://www.youtube.com/watch?v=D9pT0CHCx90
http://www.youtube.com/watch?v=puZfnzChZyA

-- Pasi

Re: DomU as Dom0?

[Daniel Stodden]

On Fri, 2010-02-12 at 02:46 -0500, Thomas Goirand wrote:
> Sassy Natan wrote:
> > OK,
> > 
> > Thanks for the answers
> > 
> > Sassy
> > 
> > On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
> > <daniel.stodden@citrix.com <mailto:daniel.stodden@citrix.com>> wrote:
> >     If you're rather looking for recursive virtualization, I don't think
> >     that's going to fly all that well either.
> > 
> >     Daniel
> 
> 
> It's called "nested virtualization" (not recursive) and there was a talk
> about it on the last Xen Summit in Shanghai. I suggest you to read the
> video:
> 
> http://www.xen.org/files/xensummit_intel09/xensummit-nested-virt.pdf
> http://www.xen.org/media/Movies/XenSummitAsia09/2009-11-19-afternoon/NestedVirtualization.MTS

Ah, nice. I didn't expect VMX emulation be actually in the works
somewhere. Cool, thanks for the link.

"Recursive" was the original term for such a beast.

Any estimates on the footprint? Small enough to be a candidate for
inclusion? It'd certainly be interesting for some applications.

Cheers,
Daniel

Re: DomU as Dom0?

[Sassy Natan]

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WOW, This topic become a hot one.

I in a middle of written an overview about virtualized the virtual.
Thanks for all the pepole who respones to this email.

I will send my papaer once I will finish it :-)

Thanks for all

Xen is really cool project!

Sassy

On Mon, Feb 15, 2010 at 12:16 PM, Daniel Stodden
<daniel.stodden@citrix.com>wrote:

> On Fri, 2010-02-12 at 02:46 -0500, Thomas Goirand wrote:
> > Sassy Natan wrote:
> > > OK,
> > >
> > > Thanks for the answers
> > >
> > > Sassy
> > >
> > > On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
> > > <daniel.stodden@citrix.com <mailto:daniel.stodden@citrix.com>> wrote:
> > >     If you're rather looking for recursive virtualization, I don't
> think
> > >     that's going to fly all that well either.
> > >
> > >     Daniel
> >
> >
> > It's called "nested virtualization" (not recursive) and there was a talk
> > about it on the last Xen Summit in Shanghai. I suggest you to read the
> > video:
> >
> > http://www.xen.org/files/xensummit_intel09/xensummit-nested-virt.pdf
> >
> http://www.xen.org/media/Movies/XenSummitAsia09/2009-11-19-afternoon/NestedVirtualization.MTS
>
> Ah, nice. I didn't expect VMX emulation be actually in the works
> somewhere. Cool, thanks for the link.
>
> "Recursive" was the original term for such a beast.
>
> Any estimates on the footprint? Small enough to be a candidate for
> inclusion? It'd certainly be interesting for some applications.
>
> Cheers,
> Daniel
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

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RE: DomU as Dom0?

[Dong, Eddie]

Daniel Stodden wrote:
> On Fri, 2010-02-12 at 02:46 -0500, Thomas Goirand wrote:
>> Sassy Natan wrote:
>>> OK,
>>> 
>>> Thanks for the answers
>>> 
>>> Sassy
>>> 
>>> On Thu, Feb 11, 2010 at 11:41 PM, Daniel Stodden
>>> <daniel.stodden@citrix.com <mailto:daniel.stodden@citrix.com>>
>>>     wrote: If you're rather looking for recursive virtualization, I
>>>     don't think that's going to fly all that well either.
>>> 
>>>     Daniel
>> 
>> 
>> It's called "nested virtualization" (not recursive) and there was a

It is just a name difference. It is actually recursivable as if the CPU is power enough.

>> talk about it on the last Xen Summit in Shanghai. I suggest you to
>> read the video: 
>> 
>> http://www.xen.org/files/xensummit_intel09/xensummit-nested-virt.pdf
>> http://www.xen.org/media/Movies/XenSummitAsia09/2009-11-19-afternoon/NestedVirtualization.MTS
> 
> Ah, nice. I didn't expect VMX emulation be actually in the works
> somewhere. Cool, thanks for the link.
> 
> "Recursive" was the original term for such a beast.
> 
> Any estimates on the footprint? Small enough to be a candidate for
> inclusion? It'd certainly be interesting for some applications.

It should be very small. Probably 2-3K LOC, we are still working on some tunning and polishing work. 

Thx, Eddie

Re: [Xen-users] RE: DomU as Dom0?

[Javier Guerra]

On Mon, Feb 15, 2010 at 11:32 AM, Dong, Eddie <eddie.dong@intel.com> wrote:
>>> It's called "nested virtualization" (not recursive) and there was a
>
> It is just a name difference. It is actually recursivable as if the CPU is power enough.

not if (as in this case) you use different requirements for each
virtualization level.  the 'real' level needs HVM support to set an
HVM DomU, where you can run Xen, but this level doesn't have HVM, so
you can only put PV DomU's there.

The KVM on KVM experiments are closer to being fully recursive.

-- 
Javier

RE: RE: [Xen-devel] DomU as Dom0?

[Dong, Eddie]

Javier Guerra wrote:
> On Mon, Feb 15, 2010 at 11:32 AM, Dong, Eddie <eddie.dong@intel.com>
> wrote: 
>>>> It's called "nested virtualization" (not recursive) and there was a
>> 
>> It is just a name difference. It is actually recursivable as if the
>> CPU is power enough. 
> 
> not if (as in this case) you use different requirements for each
> virtualization level.  the 'real' level needs HVM support to set an
> HVM DomU, where you can run Xen, but this level doesn't have HVM, so
> you can only put PV DomU's there.

You can distinguish in this way.  The term "nested" actually comes from KVM side by Alexander Graf, though I don't know why he chooses nested rather than recursive.

What the Xen summit talked and we were approaching is exactly recursive virtualization.

> 
> The KVM on KVM experiments are closer to being fully recursive.

Yes.

Eddie

Re: [Xen-devel] DomU as Dom0?

[Thiago Camargo Martins Cordeiro]

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You can run the Xen, the dom0 and some domUs whitin a KVM guest...

On 11 February 2010 17:43, Sassy Natan <sassyn@gmail.com> wrote:

> Hi,
>
>
> Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0 for
> other DomU on top of it?
>
>
>
> Thanks
>
> Sassy
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>
>

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Re: [Xen-devel] DomU as Dom0?

[Steven Maresca]

> Date: Fri, 12 Feb 2010 13:06:25 -0200
> From: Thiago Camargo Martins Cordeiro <thiagocmartinsc@gmail.com>
> Subject: Re: [Xen-devel] DomU as Dom0?
> To: Sassy Natan <sassyn@gmail.com>
> Cc: xen-devel@lists.xensource.com, Xen List
>        <xen-users@lists.xensource.com>
> Message-ID:
>        <6b7f6eb1002120706me206d81p5b211011dd21909d@mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> You can run the Xen, the dom0 and some domUs whitin a KVM guest...
>
> On 11 February 2010 17:43, Sassy Natan <sassyn@gmail.com> wrote:
>
>> Hi,
>>
>>
>> Can I run on DomU a Dom0 Kernel? So that This DomU will act as a Dom0 for
>> other DomU on top of it?
>>
>>
>>
>> Thanks
>>
>> Sassy

Yes, you can run Xen in a domU.

However, as usual the devil is in the details. Just to clarify
(because I don't believe it has been said explicitly):

It is entirely possible right now to run Xen + dom0 within an HVM
domU.  CPU support for hardware virtualization is a requirement. In
truth, this has been the case for quite some, since the Xen 3.0
series, when HVM support started to firm up around 3.0.4.   This mode
of operation presents some challenges due the hardware emulated by
qemu-dm, time skew, etc., but it has improved greatly with the latest
Xen releases.

This is the general idea of encapsulation:
Xen { dom0, domU { Xen { dom0, domU, .. } }, ... }

In general, this technique is useful for driver/hypervisor
development, but it presents some limitations:
-The nested Xen + dom0 can only support paravirtual guests.
-Finicky dom0 kernels require boot-time tweaking (I can dig up my
notes on the details if anyone is interested).
-Paravirtual I/O from the nested dom0 to the "parent" dom0 is
possible, but requires ugly driver hackery.
-Usually slow.  Very recent AMD/Intel processors, hardware assisted
paging, etc reduce the pain, but certainly not completely.
-Not what I would consider a production-ready/supportable environment.
Good for development/experimentation/education only.  There are
quirks..

The above largely applies when running Xen+dom0+domUs within a vm on
VMware / KVM / etc.

All of that said, the nested virtualization capabilities present in
KVM, those in the Xen pipeline (discussed in the summit presentation
previously mentioned), VMware, and others do open the door to
improvement in this area.

Ultimately, I would suggest that interested parties give this a try.
If needs are met, then it may be an entirely sufficient solution.  At
the very least, taking a trip down this particular rabbit hole will be
informative :)

Steve Maresca