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

[Stefan Berger]

"Daniel P. Berrange" <address@hidden> wrote on 03/01/2017 07:54:14 
AM:

> From: "Daniel P. Berrange" <address@hidden>
> To: Stefan Berger <address@hidden>
> Cc: "Dr. David Alan Gilbert" <address@hidden>, Stefan Berger/
> Watson/address@hidden, "address@hidden" <address@hidden>, "qemu-
> address@hidden" <address@hidden>, "SERBAN, CRISTINA" 
> <address@hidden>, "Xu, Quan" <address@hidden>, 
> "address@hidden" <address@hidden>, 
> "address@hidden" <address@hidden>, "SHIH, CHING C" 
> <address@hidden>
> Date: 03/01/2017 08:03 AM
> Subject: Re: [Qemu-devel] [PATCH v5 1/4] Provide support for the CUSE 
TPM
> 
> 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 (address@hidden) 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.

The vTPM running on the backend side of the vTPM proxy driver is 
essentially the same as the CUSE TPM used for QEMU. I has the same control 
channel through sockets. So on that level we would have support for the 
operations but not integrated with anything that would support container 
migration.

   Stefan


> 
> Regards,
> Daniel
> -- 
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