nested migration issues

nested migration issues

[缪天翔]

Hi all

I am doing a research project similar to "Turtles" using the nested
vmx feature of kvm. In detail, I launch a guest kvm (donated as L1) on
the underlying kvm (donated as L0) and then set up a nested guest
(donated as L2) upon the L1 guest kvm.

The problem I come up with is that I want to migrate the whole L1
guest kvm from source machine to target (that is keeping the L2 guest
running normally). And this action causes the L2 kernl to panic.

Can anybody tell me whether kvm supports this kind of nested migration
or anybody is working on the relating field?

Thanks a lot.

Re: nested migration issues

[Jan Kiszka]

On 2013-08-27 10:29, 缪天翔 wrote:
> Hi all
> 
> I am doing a research project similar to "Turtles" using the nested
> vmx feature of kvm. In detail, I launch a guest kvm (donated as L1) on
> the underlying kvm (donated as L0) and then set up a nested guest
> (donated as L2) upon the L1 guest kvm.
> 
> The problem I come up with is that I want to migrate the whole L1
> guest kvm from source machine to target (that is keeping the L2 guest
> running normally). And this action causes the L2 kernl to panic.
> 
> Can anybody tell me whether kvm supports this kind of nested migration
> or anybody is working on the relating field?

No, KVM does not support migration while nested VMX (or SVM) is enabled.
We lack userspace interfaces to export/import the required state, and
that mostly because we do not really know yet what state needs to be
made available. Specifically nVMX is still under development. Migration
support will officially follow once we feel we reached a mature state
with nesting support.

That said, if you want to play with adding such an interface yourself,
no one will stop you. It may serve as a reference for us what is
required, but you should not expect it to be merged soon.

BTW, not only migration is broken so far. Even reset does not work while
VMX is enabled. For the same reason: userspace cannot load a VCPU state
that resets all VMX states properly.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

Re: nested migration issues

[Nadav Har'El]

On Tue, Aug 27, 2013, Jan Kiszka wrote about "Re: nested migration issues":
> > Can anybody tell me whether kvm supports this kind of nested migration
> > or anybody is working on the relating field?
> 
> No, KVM does not support migration while nested VMX (or SVM) is enabled.
> We lack userspace interfaces to export/import the required state, and
> that mostly because we do not really know yet what state needs to be
> made available. Specifically nVMX is still under development. Migration
> support will officially follow once we feel we reached a mature state
> with nesting support.

Also check out https://bugzilla.kernel.org/show_bug.cgi?id=53851 for
some earlier ideas about the issue of migrating L1 complete with its
L2s.

> That said, if you want to play with adding such an interface yourself,
> no one will stop you. It may serve as a reference for us what is
> required, but you should not expect it to be merged soon.
> 
> BTW, not only migration is broken so far. Even reset does not work while
> VMX is enabled. For the same reason: userspace cannot load a VCPU state
> that resets all VMX states properly.
> 
> Jan
> 
> -- 
> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
> Corporate Competence Center Embedded Linux
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Nadav Har'El                        |       Tuesday, Aug 27 2013, 21 Elul 5773
nyh@math.technion.ac.il             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |Committee: A group of people that keeps
http://nadav.harel.org.il           |minutes and wastes hours.

Re: nested migration issues

[Kashyap Chamarthy]

On Tue, Aug 27, 2013 at 2:48 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 2013-08-27 10:29, 缪天翔 wrote:
>> Hi all
>>
>> I am doing a research project similar to "Turtles" using the nested
>> vmx feature of kvm. In detail, I launch a guest kvm (donated as L1) on
>> the underlying kvm (donated as L0) and then set up a nested guest
>> (donated as L2) upon the L1 guest kvm.
>>
>> The problem I come up with is that I want to migrate the whole L1
>> guest kvm from source machine to target (that is keeping the L2 guest
>> running normally). And this action causes the L2 kernl to panic.
>>
>> Can anybody tell me whether kvm supports this kind of nested migration
>> or anybody is working on the relating field?
>
> No, KVM does not support migration while nested VMX (or SVM) is enabled.
> We lack userspace interfaces to export/import the required state, and
> that mostly because we do not really know yet what state needs to be
> made available.

Good to know, you saved some time :-). I was about to try to test if
it works or not.

> Specifically nVMX is still under development. Migration
> support will officially follow once we feel we reached a mature state
> with nesting support.
>
> That said, if you want to play with adding such an interface yourself,
> no one will stop you. It may serve as a reference for us what is
> required, but you should not expect it to be merged soon.
>
> BTW, not only migration is broken so far. Even reset does not work while
> VMX is enabled. For the same reason: userspace cannot load a VCPU state
> that resets all VMX states properly.
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
> Corporate Competence Center Embedded Linux
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html