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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jan 20, 2016 at 10:36:41AM -0500, Stefan Berger wrote:
> "Michael S. Tsirkin" <mst@redhat.com> wrote on 01/20/2016 10:20:58 AM:
> 
> > From: "Michael S. Tsirkin" <mst@redhat.com>
> 
> > >
> > > The CUSE TPM and associated tools can be found here:
> > >
> > > https://github.com/stefanberger/swtpm
> > >
> > > (please use the latest version)
> > >
> > > To use the external CUSE TPM, the CUSE TPM should be started as follows:
> > >
> > > # terminate previously started CUSE TPM
> > > /usr/bin/swtpm_ioctl -s /dev/vtpm-test
> > >
> > > # start CUSE TPM
> > > /usr/bin/swtpm_cuse -n vtpm-test
> > >
> > > QEMU can then be started using the following parameters:
> > >
> > > qemu-system-x86_64 \
> > >    [...] \
> > >         -tpmdev cuse-tpm,id=tpm0,cancel-path=/dev/null,path=/dev/vtpm-test
> \
> > >         -device tpm-tis,id=tpm0,tpmdev=tpm0 \
> > >    [...]
> > >
> > >
> > > Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> > > Cc: Eric Blake <eblake@redhat.com>
> >
> > Before we add a dependency on this interface,
> > I'd rather see this interface supported in kernel
> > and not just in CUSE.
> 
> For using the single hardware TPM, we have the passthrough type. It's usage is
> limited.
> 
> CUSE extends the TPM character device interface with ioctl's. Behind the
> character device we can implement a TPM 1.2 and a TPM 2. Both TPM
> implementations require large amounts of code, which I don't think should go
> into the Linux kernel itself. So I don't know who would implement this
> interface inside the Linux kernel.
> 
>   Stefan
> 

BTW I'm not talking about the code - I'm talking about the interfaces here.

One way would be to add support for these interface support in the kernel.

Maybe others can be replaced with QMP events so management
can take the necessary action.

As long as this is not the case, I suspect this code will have to stay
out of tree :( We can't depend on interfaces provided solely by cuse
devices on github.



-- 
MST