Re: [PATCH] tpm: Add driver for TPM over virtio

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

On Fri, Feb 22, 2019 at 09:31:56PM +0200, Jarkko Sakkinen wrote:
> On Fri, Feb 22, 2019 at 10:23:02AM -0500, Michael S. Tsirkin wrote:
> > On Fri, Feb 22, 2019 at 12:26:10PM +0200, Jarkko Sakkinen wrote:
> > > On Thu, Feb 21, 2019 at 06:14:02PM -0800, David Tolnay wrote:
> > > > Add a config TCG_VIRTIO_VTPM which enables a driver providing the guest
> > > > kernel side of TPM over virtio.
> > > > 
> > > > Use case: TPM support is needed for performing trusted work from within
> > > > a virtual machine launched by Chrome OS.
> > > > 
> > > > Tested inside crosvm, the Chrome OS virtual machine monitor. Crosvm's
> > > > implementation of the virtio TPM device can be found in these two source
> > > > files:
> > > > 
> > > > - https://chromium.googlesource.com/chromiumos/platform/crosvm/+/18ce5713e6cb99c40aafec52b67c28ba12a44f31/devices/src/virtio/tpm.rs
> > > > - https://chromium.googlesource.com/chromiumos/platform/crosvm/+/18ce5713e6cb99c40aafec52b67c28ba12a44f31/tpm2/src/lib.rs
> > > 
> > > These files/links do not make sense for kernel testing. Please remove
> > > them from the next version.
> > 
> > To clarify generally for a virtio device we want
> > - guest support
> > - device support
> > - spec
> > 
> > If the device is implemented in qemu and guest in linux kernel,
> > then there are lots of people familiar with these
> > programming environments, so sometimes we merge
> > guest and host code even if spec isn't written up at all.
> > 
> > If you don't want to do that there's a small number of people who can
> > properly review code, e.g. I don't think lots of people on this list are
> > familiar with crosvm.  One way to address this would be to build a QEMU
> > implementation. Another would be to write up a spec.  You can do both
> > too :)
> 
> I don't really understand your arguments.
> 
> /Jarkko

Jarkko, I am not making any argument at all.

I am trying to suggest ways for this driver to get upstream.

And I am saying that while I agree availability of an implementation in
crosvm isn't sufficient, availability of a software device
implementation in QEMU is not an absolute prerequisite for including a
virtio driver in Linux.  If there's a virtio spec explaining how to
write one, that can be enough.

-- 
MST