On 5/12/23 12:22, Ross Philipson wrote:
On 5/12/23 07:43, Matthew Garrett wrote:
On Thu, May 04, 2023 at 02:50:22PM +0000, Ross Philipson wrote:
The Secure Launch MLE environment uses PCRs that are only accessible
from
the DRTM locality 2. By default the TPM drivers always initialize the
locality to 0. When a Secure Launch is in progress, initialize the
locality to 2.
This looks correct in itself, but looking at the CRB driver code I don't
think locality support is actually implemented. Are there any SL systems
using CRB?
We have never seen a system that supports CRB other than some firmware
TPMs that don't work with TXT in the first place. CRB is unexplored
territory at this point.
So there is often confusion over the CRB interface. If you ask an ARM
person, they will describe a door-bell, general purpose memory interface
that has no support for locality. That interface is described in the
TCG's Mobile TPM interface. Though there is work in progress to address
this. Now if you speak with an x86 person, they will describe a
state-based command-response mechanism using MMIO registers which has
locality support. That interface is described in the TCG PC Client
specification.
As to whether there are devices with CRB and TXT. I have seen talk on
the tboot mailing list that there exist an Intel client devices that has
an Intel-PTT fTPM using the PC Client CRB interface and Intel-TXT. I
myself have never seen one, so I could not point you at a SKU/Part No.
for such a device. If someone has such a device and willing to help,
drop me a line and I would be glad to work with them to get this tested.
v/r,
dps
