On Wed, 7 Jun 2023 at 18:10, Jan Kiszka <jan.kiszka@xxxxxxxxxxx> wrote: > > On 07.06.23 10:25, Ilias Apalodimas wrote: > > Hi Sumit, > > > > On Wed, 7 Jun 2023 at 10:25, Sumit Garg <sumit.garg@xxxxxxxxxx> wrote: > >> > >> Hi Ilias, > >> > >> On Wed, 7 Jun 2023 at 12:05, Ilias Apalodimas > >> <ilias.apalodimas@xxxxxxxxxx> wrote: > >>> > >>> Hi Jan, > >>> > >>> [...] > >>> > >>>>>>>> > >>>>> ... > >>>>>>> > >>>>>>> I think we have a probe ordering issue with this driver: > >>>>>>> efivarfs_fill_super() may be called before the TEE bus was probed, thus > >>>>>>> with the default efivar ops still registered. And that means > >>>>>>> efivar_supports_writes() will return false, and the fs declares itself > >>>>>>> as readonly. I've seen systemd mounting it r/o initialling, and you need > >>>>>>> to remount the fs to enable writability. > >>>>>>> > >>>>>>> Is there anything that could be done to re-order things reliably, probe > >>>>>>> the tee bus earlier etc.? > >>>>>> > >>>>>> This driver has a dependency on user-space daemon: tee-supplicant to > >>>>>> be running for RPMB access. So once you start that daemon the > >>>>>> corresponding device will be enumerated on the TEE bus and this driver > >>>>>> probe will be invoked. So I would suggest you to load this daemon very > >>>>>> early in the boot process or better to make it a part of initramfs. > >>>>>> > >>>>> > >>>>> That is not the point, really. > >>>>> > >>>>> If this dependency exists, the code should be aware of that, and made > >>>>> to work correctly in spite of it. Requiring a module to be part of > >>>>> initramfs is not a reasonable fix. > >>>> > >>>> In fact, I've tested a non-modularized build as well, just to exclude > >>>> that issue. The daemon dependency is more likely the problem here. > >>>> > >>>>> > >>>>> IIUC, this also means that the efivar ops are updated while there is > >>>>> already a client. This seems less than ideal as well > >>> > >>> As Sumit pointed out, the 'device' won't be available from OP-TEE > >>> until the supplicant is up and running and as a result, the module > >>> _probe() function won't run. Unfortunately, this isn't something we > >>> can avoid since the supplicant is responsible for the RPMB writes. > >>> The only thing I can think of is moving parts of the supplicant to the > >>> kernel and wiring up the RPC calls for reading/writing data to the > >>> eMMC subsystem. There was another discussion here [0] requesting the > >>> same thing for different reasons. But unless I am missing something > >>> this won't solve the problem completely either. You still have a > >>> timing dependency of "when did the RT callbacks change" -- "when was > >>> my efivarfs mounted". > >> > >> With the RPMB writes wired through the kernel [1], the only dependency > >> left is when do you load the tee-stmm-efi driver to have real EFI > >> runtime variables support. IMO, tee-stmm-efi driver should be built-in > >> to support systems without initramfs. The distro installers may choose > >> to bundle it in initramfs. Do you still see a timing dependency with > >> this approach? > > > > No I don't, this will work reliably without the need to remount the efivarfs. > > As you point out you will still have this dependency if you end up > > building them as modules and you manage to mount the efivarfs before > > those get inserted. Does anyone see a reasonable workaround? > > Deceiving the kernel and making the bootloader set the RT property bit > > to force the filesystem being mounted as rw is a nasty hack that we > > should avoid. Maybe adding a kernel command line parameter that says > > "Ignore the RTPROP I know what I am doing"? I don't particularly love > > this either, but it's not unreasonable. > > In the context of https://github.com/OP-TEE/optee_os/issues/6094, > basically this issue mapped on reboot/shutdown, I would really love to > see the unhandy tee-supplicant daemon to be overcome. I have seen this error before and it has been on my todo list. So I have tried to fix it here [1]. Feel free to test it and let me know if you see any further issues. [1] https://lkml.org/lkml/2023/6/7/927 -Sumit > > Jan > > -- > Siemens AG, Technology > Competence Center Embedded Linux >
