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

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Date:	Wed, 13 Aug 2014 22:14:53 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Theodore Ts'o" <tytso@....edu>, kvm list <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Bandan Das <bsd@...hat.com>, Andrew Honig <ahonig@...gle.com>
Subject: Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some
 from kvm

On Wed, Aug 13, 2014 at 7:41 PM, H. Peter Anvin <hpa@...or.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
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