Mailing List Archive

On Thu, Sep 20, 2012 at 09:11:44AM +0200, Lukas Laukamp wrote:
> Hello all,
>
> I have a simple user question but it's very technical and related to
> the Xen core. Does KVM and VirtualBox work in a Xen Dom0 with Xen
> 4.2? So I would like to create a VM Host for deploying VM templates
> which are compatible to the most solutions and host systems and I
> think that Xen, KVM/QEmu and VirtualBox are the best choice for
> this.
>
> Would be great when this is possible or could be implemented. Hope
> that someone can give me an answer.
>

Nope, KVM or VirtualBox won't work in Xen dom0.

But you can use Xen Nested Hardware Virtualization and run KVM/VirtualBox in Xen HVM guest.
This is a "tech preview" currently.

-- Pasi


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Am 2012-09-20 09:36, schrieb Pasi Kärkkäinen:
> On Thu, Sep 20, 2012 at 09:11:44AM +0200, Lukas Laukamp wrote:
>> Hello all,
>>
>> I have a simple user question but it's very technical and related to
>> the Xen core. Does KVM and VirtualBox work in a Xen Dom0 with Xen
>> 4.2? So I would like to create a VM Host for deploying VM templates
>> which are compatible to the most solutions and host systems and I
>> think that Xen, KVM/QEmu and VirtualBox are the best choice for
>> this.
>>
>> Would be great when this is possible or could be implemented. Hope
>> that someone can give me an answer.
>>
>
> Nope, KVM or VirtualBox won't work in Xen dom0.
>
> But you can use Xen Nested Hardware Virtualization and run
> KVM/VirtualBox in Xen HVM guest.
> This is a "tech preview" currently.
>
> -- Pasi

Hello,

ok, this would be possible with Xen 4.2? And would it be possible to
implement something that KVM and VirtualBox work in a Xen Dom0? Is this
a task for the Xen development or something for the Linux kernel,, KVM
or VirtualBox?

Best Regards

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On Thu, Sep 20, 2012 at 09:44:41AM +0200, Lukas Laukamp wrote:
> Am 2012-09-20 09:36, schrieb Pasi Kärkkäinen:
> >On Thu, Sep 20, 2012 at 09:11:44AM +0200, Lukas Laukamp wrote:
> >>Hello all,
> >>
> >>I have a simple user question but it's very technical and related to
> >>the Xen core. Does KVM and VirtualBox work in a Xen Dom0 with Xen
> >>4.2? So I would like to create a VM Host for deploying VM templates
> >>which are compatible to the most solutions and host systems and I
> >>think that Xen, KVM/QEmu and VirtualBox are the best choice for
> >>this.
> >>
> >>Would be great when this is possible or could be implemented. Hope
> >>that someone can give me an answer.
> >>
> >
> >Nope, KVM or VirtualBox won't work in Xen dom0.
> >
> >But you can use Xen Nested Hardware Virtualization and run
> >KVM/VirtualBox in Xen HVM guest.
> >This is a "tech preview" currently.
> >
> >-- Pasi
>
> Hello,
>
> ok, this would be possible with Xen 4.2?
>

In Xen 4.2.0 I think Nested Virt should work on AMD CPUs,
but Intel CPUs require some additional patches that aren't yet in 4.2 branch.

> And would it be possible to implement something that KVM and VirtualBox work in a Xen Dom0?
>

Why do you want to run them in dom0 ?

> Is this a task for the Xen development or something for the Linux
> kernel,, KVM or VirtualBox?
>

I think it *might* be possible when Xen PVH (Hybrid) is merged to Xen 4.3,
which basically allows running Xen dom0 in HVM container.

-- Pasi


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Am 2012-09-20 09:52, schrieb Pasi Kärkkäinen:
> On Thu, Sep 20, 2012 at 09:44:41AM +0200, Lukas Laukamp wrote:
>> Am 2012-09-20 09:36, schrieb Pasi Kärkkäinen:
>> >On Thu, Sep 20, 2012 at 09:11:44AM +0200, Lukas Laukamp wrote:
>> >>Hello all,
>> >>
>> >>I have a simple user question but it's very technical and related
>> to
>> >>the Xen core. Does KVM and VirtualBox work in a Xen Dom0 with Xen
>> >>4.2? So I would like to create a VM Host for deploying VM
>> templates
>> >>which are compatible to the most solutions and host systems and I
>> >>think that Xen, KVM/QEmu and VirtualBox are the best choice for
>> >>this.
>> >>
>> >>Would be great when this is possible or could be implemented. Hope
>> >>that someone can give me an answer.
>> >>
>> >
>> >Nope, KVM or VirtualBox won't work in Xen dom0.
>> >
>> >But you can use Xen Nested Hardware Virtualization and run
>> >KVM/VirtualBox in Xen HVM guest.
>> >This is a "tech preview" currently.
>> >
>> >-- Pasi
>>
>> Hello,
>>
>> ok, this would be possible with Xen 4.2?
>>
>
> In Xen 4.2.0 I think Nested Virt should work on AMD CPUs,
> but Intel CPUs require some additional patches that aren't yet in 4.2
> branch.
>
>> And would it be possible to implement something that KVM and
>> VirtualBox work in a Xen Dom0?
>>
>
> Why do you want to run them in dom0 ?
>
>> Is this a task for the Xen development or something for the Linux
>> kernel,, KVM or VirtualBox?
>>
>
> I think it *might* be possible when Xen PVH (Hybrid) is merged to Xen
> 4.3,
> which basically allows running Xen dom0 in HVM container.
>
> -- Pasi

Hello,

I googled for xen Hybrid, but have question if I understand it correct.
Now the Dom0 is a PV Guest. With Xen Hybrid the Dom0 can run as a HVM
with PV features on the hypervisor. This would make it possible because
of nested virtualization that KVM and VirtualBox run inside dom0 right?

And my second question would be: Is the aim of Xen hybrid to bring Dom0
support to more OSes?

Best Regards

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On Thu, Sep 20, 2012 at 2:44 PM, Lukas Laukamp <lukas@laukamp.me> wrote:

> And would it be possible to
> implement something that KVM and VirtualBox work in a Xen Dom0?

> Is this a
> task for the Xen development or something for the Linux kernel,, KVM or
> VirtualBox?

Since it looks like you're a user and not a developer, I'd actually
suggest you rethink your requirements and find ways to implement it
using available solutions.

For example, you said you want to "create a VM Host for deploying VM
templates which are compatible to the most solutions". If the
templates are Linux, it's much easier to create one template that
suits all. Some things to watch out for:
- disk driver. Ubuntu loads most disk driver by default, but for other
distros (e.g. Centos) you might need to force drivers (xen front block
driver, virtio, etc) to be included in initrd by modifying
/etc/modprobe.conf or similar regardles which driver is currently
active
- disk naming. Use LABEL or UUID whenever possible
- filesystem for /boot. To be safe, use a separate /boot partition,
and use ext2/ext3, since some versions of pygrub do not support ext4.

If you follow that, you should be able to use the same image on
virtualbox, vmware, xen PV (with vfb enabled) or HVM. If you need more
help creating this template, xen-users will be a more appropriate
place to ask.

Another option, if your machine is dedicated for this purpose, is to
run native linux with kvm and virtualbox installed (you can have them
both installed, just not used at the same time), and install xen
inside a VM. That way you can still test everything except xen HVM.

--
Fajar

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On Thu, Sep 20, 2012 at 10:03:43AM +0200, Lukas Laukamp wrote:
> >
> >I think it *might* be possible when Xen PVH (Hybrid) is merged to
> >Xen 4.3,
> >which basically allows running Xen dom0 in HVM container.
> >
> >-- Pasi
>
> Hello,
>
> I googled for xen Hybrid, but have question if I understand it
> correct. Now the Dom0 is a PV Guest.
>

Correct.

> With Xen Hybrid the Dom0 can run as a HVM with PV features on the hypervisor.
>

PVH dom0 is basicly PV dom0 in HVM container. It's more PV than HVM.

> This would make it possible because of nested virtualization that KVM and VirtualBox
> run inside dom0 right?
>

Yes, but PVH doesn't enable nested virt automatically, that'll require some extra patches.

> And my second question would be: Is the aim of Xen hybrid to bring
> Dom0 support to more OSes?
>

The purpose of PVH dom0 is to be able to utilize HAP (Hardware Assisted Paging)
in dom0, and also lowering syscall overhead for 64bit dom0.

So it's about optimizations.
See Mukesh's presentation about PVH/Hybrid from XenSummit North America 2012.

-- Pasi


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Am 2012-09-20 10:37, schrieb Pasi Kärkkäinen:
> On Thu, Sep 20, 2012 at 10:03:43AM +0200, Lukas Laukamp wrote:
>> >
>> >I think it *might* be possible when Xen PVH (Hybrid) is merged to
>> >Xen 4.3,
>> >which basically allows running Xen dom0 in HVM container.
>> >
>> >-- Pasi
>>
>> Hello,
>>
>> I googled for xen Hybrid, but have question if I understand it
>> correct. Now the Dom0 is a PV Guest.
>>
>
> Correct.
>
>> With Xen Hybrid the Dom0 can run as a HVM with PV features on the
>> hypervisor.
>>
>
> PVH dom0 is basicly PV dom0 in HVM container. It's more PV than HVM.
>
>> This would make it possible because of nested virtualization that
>> KVM and VirtualBox
>> run inside dom0 right?
>>
>
> Yes, but PVH doesn't enable nested virt automatically, that'll
> require some extra patches.
>
>> And my second question would be: Is the aim of Xen hybrid to bring
>> Dom0 support to more OSes?
>>
>
> The purpose of PVH dom0 is to be able to utilize HAP (Hardware
> Assisted Paging)
> in dom0, and also lowering syscall overhead for 64bit dom0.
>
> So it's about optimizations.
> See Mukesh's presentation about PVH/Hybrid from XenSummit North
> America 2012.
>
> -- Pasi
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Hello,

thanks for our replies Fajar and Pasi. My questions are replied now. I
thought it would be comfortable to have them all on one host, we will
see whether it's possible in future with PVH.

Best Regards

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