On Sat, Oct 02, 2021 at 07:20:22AM -0700, Andi Kleen wrote:

On 10/2/2021 4:14 AM, Greg Kroah-Hartman wrote:

quoted

On Sat, Oct 02, 2021 at 07:04:28AM -0400, Michael S. Tsirkin wrote:

quoted

On Fri, Oct 01, 2021 at 08:49:28AM -0700, Andi Kleen wrote:

quoted

quoted

   Do you have a list of specific drivers and kernel options that you
feel you now "trust"?

For TDX it's currently only virtio net/block/console

But we expect this list to grow slightly over time, but not at a high rate
(so hopefully <10)

Well there are already >10 virtio drivers and I think it's reasonable
that all of these will be used with encrypted guests. The list will
grow.

What is keeping "all" drivers from being on this list?

It would be too much work to harden them all, and it would be pointless
because all these drivers are never legitimately needed in a virtualized
environment which only virtualize a very small number of devices.

Why would you not want to properly review and fix up all kernel drivers?
That feels like you are being lazy.

What exactly are you meaning by "harden"?  Why isn't it automated?  Who
is doing this work?  Where is it being done?

Come on, you have a small number of virtio drivers, to somehow say that
they are now divided up into trusted/untrusted feels very very odd.

Just do the real work here, everyone will benefit, including yourself.

quoted

  How exactly are
you determining what should, and should not, be allowed?

Everything that has had reasonable effort at hardening can be added. But if
someone proposes to add a driver that should trigger additional scrutiny in
code review. We should also request them to do some fuzzing.

You can provide that fuzzing right now, why isn't syzbot running on
these interfaces today?

And again, what _exactly_ do you all mean by "hardening" that has
happened?  Where is that documented and who did that work?

quoted

And why not just put all of that into userspace and have it pick and
choose?  That should be the end-goal here, you don't want to encode
policy like this in the kernel, right?

How would user space know what drivers have been hardened? This is really
something that the kernel needs to determine. I don't think we can outsource
it to anyone else.

It would "know" just as well as you know today in the kernel.  There is
no difference here.

Just do the real work here, and "harden" all of the virtio drivers
please.  What prevents that?

Also BTW of course user space can still override it, but really the defaults
should be a kernel policy.

There's also the additional problem that one of the goals of confidential
guest is to just move existing guest virtual images into them without much
changes. So it's better for such a case if as much as possible of the policy
is in the kernel. But that's more a secondary consideration, the first point
is really the important part.

Where exactly are all of these "goals" and "requirements" documented and
who is defining them and forcing them on us without actually doing any
of the work involved?

thanks,

greg k-h
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