Re: [PATCH] tpm: Add driver for TPM over virtio

On Fri, Feb 22, 2019 at 11:59:23PM +0200, Jarkko Sakkinen wrote:

On Fri, Feb 22, 2019 at 02:31:37PM -0700, Jason Gunthorpe wrote:

quoted

On Fri, Feb 22, 2019 at 04:16:01PM -0500, Michael S. Tsirkin wrote:

quoted

On Fri, Feb 22, 2019 at 07:30:16AM -0800, James Bottomley wrote:

quoted

On Thu, 2019-02-21 at 18:14 -0800, David Tolnay wrote:

quoted

Add a config TCG_VIRTIO_VTPM which enables a driver providing the
guest kernel side of TPM over virtio.

What's the use case for using this over the current non-virtio vTPM?. 
I always thought virtio was about guest to host transport efficiency,
but the phsical TPM, being connected over a very slow bus, is about as
inefficient as you can get in that regard, so why do we need to use
virtio to drive the virtual one?

I can't say for sure about TPM.

But generally there are many reasons to do virtio rather than emulating
a hardware device.

We already have a xen 'virtioish' TPM driver, so I don't think there
is a good reason to block a virtio driver if someone cares about
it. There are enough good reasons to prefer virtio to other options,
IMHO.

Provided it meets the general requirements for new virtio stuff you
outlined.

Yeah, absolutely we can consider this.

For me it boils down to testing and documentation part.

No plans to merge code that I'm unable to run...

/Jarkko

I do this sometimes. One can't require samples for all supported
hardware. If I can check that code matches spec, I might settle for
that.

-- 
MST