Hi Mikko, On 10:09 Wed 29 May , Mikko Rapeli wrote: > On Wed, May 29, 2024 at 10:56:04AM +0530, Sumit Garg wrote: > > On Tue, 28 May 2024 at 15:00, Mikko Rapeli <mikko.rapeli@xxxxxxxxxx> wrote: > > > On Mon, May 27, 2024 at 03:24:01PM +0200, Jens Wiklander wrote: > > > > On Mon, May 27, 2024 at 3:00 PM Jerome Forissier > > > > <jerome.forissier@xxxxxxxxxx> wrote: > > > > > On 5/27/24 14:13, Jens Wiklander wrote: > > > Outside of these patches, I think the optee RPC setup with fTPM TA is one area which > > > currently requires tee-supplicant to be started. Detecting the existence of TPM before > > > kernel drivers are loaded is possible via the exported EFI logs from firmware to kernel > > > or ACPI TPM2 table entry, and detecting optee and thus starting tee-supplicant in userspace too. > > > > One thing I am trying to find an answer about is why do we need to > > defer tee-supplicant launch if it's bundled into initrd? Once you > > detect OP-TEE then tee-supplicant should be launched unconditionally. > > As per your example below, the motivation here seems to be the TPM2 > > device dependent on RPMB backend but what if other future systemd > > services come up and depend on other services offered by > > tee-supplicant? > > There is an annoying depedency between firmware side optee and TAs, and kernel optee driver, > tee-supplicant in userspace and kernel TA drivers like fTPM. > > Kernel fTPM driver and fTPM TA require tee-supplicant in userspace for RPMB, RPC etc. > > This patch series is adding kernel side support for RPMB handling so that the dependency to > tee-supplicant in userspace can be removed. For fTPM use case, there is still the optee RPC > buffer setup which currently requires tee-supplicant in userspace or fTPM TA will panic. > > So yes, currently, tee-supplicant must be started. But it would be great if kernel drivers > and firmware optee trusted applications would not depend on tee-supplicant running in userspace. > The startup sequence is really tricky to get right. My fTPM use case is using the TPM device > to encrypt rootfs and thus all SW components including tee-supplicant need to run early in > initramfs. Currently also switch from initramfs to main rootfs requires unloading > fTPM kernel driver and stopping tee-supplicant in initrd, and then starting tee-supplicant > and loading fTPM kernel driver from main rootfs. udev and automatic module loading for > fTPM can not be used due to the tee-supplicant userspace dependency. I decided to build fTPM as buildin-TA into OP-TEE. RPMB routing is already implemented in u-boot so it can already write PCR registers. With this series and the required changes in OP-TEE and a compiled in fTPM kernel driver and systemd v256 it is possible to use the fTPM in the initrd without tee-supplicant. Maybe this information is helpful to you, regards Manuel
