Can it be done: Xen inside a KVM guest

mpkossen

I've been searching around for people having experience with this. I've also tried it myself (but it didn't work). I want to run Xen inside a KVM Guest. Just Xen PV, not HVM, obviously. I could install it just fine but it doesn't complete the boot and seems to hang at completely different points.

Why would I want this? For fun and testing purposes

Anyway, the real question is: has anybody done it before? And if yes: how?

erhwegesrgsr

Try Xenner ;-)

zhuanyi

I am pretty sure I saw @AnothnySmith got this kind of setup up and running before, but not sure the details.

Ash_Hawkridge

OpenVZ and Xen run fine inside KVM

Rallias

It can be done. You need to enable hardware virtualization passthrough to use HVM. I'm not sure the exact name of the feature.

You'd probably need a virtual "real" ethernet card. I'm not too keen on it tho.

ShardHostSarah

You'll need to enable nested virtualisation. There are a number of guides for KVM available online.

mpkossen

@ShardHost said: You'll need to enable nested virtualisation. There are a number of guides for KVM available online.

Also for just Xen PV?

Rallias

@mpkossen said: Also for just Xen PV?

No. You don't need the virtualization extensions for PV.

mpkossen

@Rallias said: No. You don't need the virtualization extensions for PV.

I thought so, so that can't be it then

I'll toy around, see how far I can get. Hopefully somebody else has some experience.

mpkossen

FACEPALM: doesn't work with VirtIO

ShardHostSarah

Sorry missed PV

Maounique

I tried to boot xen with centos 5 inside a full virtualized machine for Xen-PV with the same results, hanging.
Debian worked tho. I was using virtualbox and blamed it on that at first, later tried in a proxmox and had the same failure.
I think it is something centos 5 specific.

Mon5t3r

i just running this successfully (but not fully satisfied with the performances) :

• OVZ inside KVM
• KVM inside KVM (nested KVM)
• LXC inside KVM and LXC inside KVM inside KVM
• HVM/PV inside KVM (but for HVM you still need the nested parameters enabled in your kernel)

mpkossen

Thanks for the responses, guys! It seems to be running smooth now I'm going to test the performance, but I'm glad it works out of the box on Ubuntu (though not with VirtIO).

raphaelluciano

Hi @mpkossen,
I'm trying to do the same thing (run a Xen VM guest on a KVM fisical host) with no success until now. Both, host and guest, are ubuntu 64bits. When I try to boot the xen guest, I get some error, something like: Code 55 14 f3 33 f5 78 ...

I couldn't understand what did you do in order to make it work. Can you give a little help on it?

Thanks in advance.
Have a good one!

angstrom

@raphaelluciano said:
Hi @mpkossen,
I'm trying to do the same thing (run a Xen VM guest on a KVM fisical host) with no success until now. Both, host and guest, are ubuntu 64bits. When I try to boot the xen guest, I get some error, something like: Code 55 14 f3 33 f5 78 ...

I couldn't understand what did you do in order to make it work. Can you give a little help on it?

Thanks in advance.
Have a good one!

Bravo for the necro.

svmo

@Mon5t3r said:
i just running this successfully (but not fully satisfied with the performances) :

• OVZ inside KVM
• KVM inside KVM (nested KVM)
• LXC inside KVM and LXC inside KVM inside KVM
• HVM/PV inside KVM (but for HVM you still need the nested parameters enabled in your kernel)

To add to the list:

• KVM inside LXD
  (you can take a snapshot of your whole KVM environment and migrate it to a different server)

randvegeta

what's the performance hit on nest virtualization?

WSS

@randvegeta said:
what's the performance hit on nest virtualization?

Six.

AuroraZ

@randvegeta said:
what's the performance hit on nest virtualization?

Not too much if you pass everything straight through.

randvegeta

WSS said: Six.

Imposibru!!

Janevski

@raphaelluciano said:
something like: Code 55 14 f3 33 f5 78 ...