On Thu, 2019-02-21 at 18:14 -0800, David Tolnay wrote: > Add a config TCG_VIRTIO_VTPM which enables a driver providing the > guest kernel side of TPM over virtio. What's the use case for using this over the current non-virtio vTPM?. I always thought virtio was about guest to host transport efficiency, but the phsical TPM, being connected over a very slow bus, is about as inefficient as you can get in that regard, so why do we need to use virtio to drive the virtual one? > Use case: TPM support is needed for performing trusted work from > within a virtual machine launched by Chrome OS. The current vTPM does this, what's the use case for your special one? > 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/+/18ce > 5713e6cb99c40aafec52b67c28ba12a44f31/devices/src/virtio/tpm.rs > - https://chromium.googlesource.com/chromiumos/platform/crosvm/+/18ce > 5713e6cb99c40aafec52b67c28ba12a44f31/tpm2/src/lib.rs > > and is currently backed by the libtpm2 TPM simulator: So is the reason simply that crosvm did vTPM emulation differently from qemu and thus needs a different driver? James
