Re: [Qemu-devel] [PATCH v5 1/4] Provide support for the CUSE TPM

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Mar 01, 2017 at 07:25:28AM -0500, Stefan Berger wrote:
> On 06/16/2016 04:25 AM, Daniel P. Berrange wrote:
> > On Thu, Jun 16, 2016 at 09:05:20AM +0100, Dr. David Alan Gilbert wrote:
> > > * Stefan Berger (stefanb@linux.vnet.ibm.com) wrote:
> > > > On 06/15/2016 03:30 PM, Dr. David Alan Gilbert wrote:
> > > <snip>
> > > 
> > > > > So what was the multi-instance vTPM proxy driver patch set about?
> > > > That's for containers.
> > > Why have the two mechanisms? Can you explain how the multi-instance
> > > proxy works; my brief reading when I saw your patch series seemed
> > > to suggest it could be used instead of CUSE for the non-container case.
> > One of the key things that was/is not appealing about this CUSE approach
> > is that it basically invents a new ioctl() mechanism for talking to
> > a TPM chardev. With in-kernel vTPM support, QEMU probably doesn't need
> > to have any changes at all - its existing driver for talking to TPM
> 
> We still need the control channel with the vTPM to reset it upon VM reset,
> for getting and setting the state of the vTPM upon snapshot/suspend/resume,
> changing locality, etc.

You ultimately need the same mechanisms if using in-kernel vTPM with
containers as containers can support snapshot/suspend/resume/etc too.

Regards,
Daniel
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