On Wed, Jan 20, 2016 at 11:06:45AM -0500, Stefan Berger wrote: > "Michael S. Tsirkin" <m...@redhat.com> wrote on 01/20/2016 10:58:02 AM: > > > From: "Michael S. Tsirkin" <m...@redhat.com> > > > > > 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 thinkshould > > > 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. > > Why is that? I know that the existing ioctls cannot be modified anymore once > QEMU accepts the code. So I don't understand it. Some of the ioctls are only > useful when emulating a hardware device,
Maybe they can be replaced with QMP events? These could be emitted unconditionally, and ignored by management in passthrough case. > so there's no need for them in a > kernel interface unless one was to put the vTPM code into the Linux kernel, > but > I don't see that this is happening. What is better about a kernel interface > versus one implemented by a project on github assuming that the existing > ioctls > are stable? What is the real reason here? > > Stefan > That someone went to the trouble of reviewing the interface for long-term maintainability, portability etc. That it obeys some existing standards for API use, coding style etc and will continue to. In other words, kernel is already a dependency for QEMU. > > > > > > > > -- > > MST > > >
