Re: nested migration issues

[Jan Kiszka <jan.kiszka@siemens.com>]

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

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