On Wed, Jan 20, 2016 at 05:58:02PM +0200, Michael S. Tsirkin wrote: > On Wed, Jan 20, 2016 at 10:36:41AM -0500, Stefan Berger wrote: > > "Michael S. Tsirkin" <m...@redhat.com> wrote on 01/20/2016 10:20:58 AM: > > > > > From: "Michael S. Tsirkin" <m...@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 <stef...@linux.vnet.ibm.com> > > > > Cc: Eric Blake <ebl...@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.
The kernel already has a userspace device interface for TPMs doesn't it - it is what our existing 'tpm-passthrough' backend in QEMU surely uses. If swtpm is going to the trouble of providing device node emulation with CUSE, I would have thought it could emulate the same interface as the existing kernel TPM device nodes, thus removing the need for any extra driver in QEMU ? Otherwise it doesn't seem like there's much point in using CUSE, as opposed to a general userspace RPC protocol that doesn't need kernel support at all. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
