Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm

Andy Lutomirski
2014-08-14T05:15:17Z

On Wed, Aug 13, 2014 at 7:41 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 08/13/2014 11:44 AM, H. Peter Anvin wrote:
>> On 08/13/2014 11:33 AM, Andy Lutomirski wrote:
>>>
>>> As for doing arch_random_init after clone/migration, I think we'll
>>> need another KVM extension for that, since, AFAIK, we don't actually
>>> get notified that we were cloned or migrated. That will be
>>> nontrivial. Maybe we can figure that out at KS, too.
>>>
>>
>> We don't need a reset when migrated (although it might be a good idea
>> under some circumstances, i.e. if the pools might somehow have gotten
>> exposed) but definitely when cloned.
>>
>
> But yes, we need a notification. For obvious reasons there is no
> suspend event (one can snapshot a running VM) but we need to be notified
> upon wakeup, *or* we need to give KVM a way to update the necessary state.

This could presumably use the interrupt mechanism on virtio-rng if
we're willing to depend on having host support for virtio-rng.

v6 (coming in a few minutes) will at least get it right when the
kernel goes through the resume path (i.e. not KVM/QEMU suspend, and
maybe not S0ix either).

--Andy