Re: [PATCH 2/2] tpm: add backend for mssim

[Stefan Berger]

On 12/16/22 05:27, Daniel P. Berrangé wrote:
> On Thu, Dec 15, 2022 at 03:53:43PM -0500, Stefan Berger wrote:
> > On 12/15/22 15:30, James Bottomley wrote:
> > > On Thu, 2022-12-15 at 15:22 -0500, Stefan Berger wrote:
> > > > On 12/15/22 15:07, James Bottomley wrote:
> > > [...]
> > > > > don't really have much interest in the migration use case, but I
> > > > > knew it should work like the passthrough case, so that's what I
> > > > > tested.
> > > >
> > > > I think your device needs to block migrations since it doesn't handle
> > > > all migration scenarios correctly.
> > >
> > > Passthrough doesn't block migrations either, presumably because it can
> > > also be made to work if you know what you're doing.  I might not be
> >
> > Don't compare it to passthrough, compare it to swtpm. It should
> > have at least the same features as swtpm or be better, otherwise
> > I don't see why we need to have the backend device in the upstream
> > repo.
>
> James has explained multiple times that mssim is a beneficial
> thing to support, given that it is the reference implementation
> of TPM2. Requiring the same or greater features than swtpm is
> an unreasonable thing to demand.

Nevertheless it needs documentation and has to handle migration scenarios 
either via a blocker or it has to handle them all correctly. Since it's 
supposed to be a TPM running remote you had asked for TLS support iirc.

  Stefan

> With regards,
> Daniel