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

["Stefan Berger" <stefanb@us.ibm.com>]

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"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



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