Re: [Qemu-devel] [PATCH 0/7] Provide support for the software TPM emulator

[Dr. David Alan Gilbert]

* Daniel P. Berrange (address@hidden) wrote:
> On Fri, Mar 31, 2017 at 04:10:09PM +0300, Amarnath Valluri wrote:
> > Briefly, Theses set of patches introduces:
> >  - new TPM backend driver to support software TPM emulators(swtpm(1)).
> >  - and few supported fixes/enhancements/cleanup to existing tpm backend 
> > code.
> > 
> > The similar idea was initiated earliar(2) by Stefan Berger(CCed) with 
> > slightly
> > different approach, using CUSE. As swtpm has excellent support for unix 
> > domain
> > sockets, hence this implementation uses unix domain sockets to communicate 
> > with
> > swtpm.
> > 
> > When Qemu is configured with 'emulator' tpm backend, it spawns 'swtpm' and
> > communicates its via Unix domain sockets.
> 
> I'm not convinced that having QEMU spawning swtpm itself is a desirable
> approach, as it means QEMU needs to have all the privileges that swtpm
> will need, so that swtpm can inherit them. At the very least I think we
> need to have a way to disable this spawning, so it can connect to a
> pre-existing swtpm process that's been spawned ahead of time. This will
> let us have stricter privilege separation.

I agree, just letting something external start the swtpm and using
a chardev to talk to it would seem to work wouldn't it?

However, generally I prefer this mechanism of avoiding CUSE.

Dave


> Regards,
> Daniel
> -- 
> |: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
> |: http://libvirt.org              -o-             http://virt-manager.org :|
> |: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/ :|
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK