Am 30.06.25 um 14:17 schrieb Marco Felsch: > Hi Frieder, > > On 25-06-30, Frieder Schrempf wrote: >> Hi Marco, >> >> Am 27.06.25 um 10:46 schrieb Marco Felsch: >>> Hi, >>> >>> your e-mail configuration mixed my e-mail with your answer, which makes >>> it hard to read. Can you please check the quoting next time :) >>> >>> On 25-06-27, Pankaj Gupta wrote: >>>>>> Add driver for enabling MU based communication interface to >>>> secure-enclave. >>>>>> >>>>>> NXP hardware IP(s) for secure-enclaves like Edgelock Enclave(ELE), are >>>>>> embedded in the SoC to support the features like HSM, SHE & V2X, using >>>>>> message based communication interface. >>>>>> >>>>>> The secure enclave FW communicates with Linux over single or multiple >>>>>> dedicated messaging unit(MU) based interface(s). >>>>>> Exists on i.MX SoC(s) like i.MX8ULP, i.MX93, i.MX95 etc. >>>> >>>>> You write single or multiple MUs are possible. I'm aware that the i.MX93 >>>>> has two MUs one for the secure and one for the non-secure world. But I'm >>>>> really concerned about the fact that both MUs can't be used at the same time >>>>> from both world: >>>> >>>> Yes, you are correct. >>>> >>>> Fix is still work in progress. >>> >>> So after ~6 months no fix is available :( >>> >>>>> Also how is the secure and non-secure world talking to the ELE if there is >>>>> only one MU as you have written? >>>> >>>> Till the fix is WIP, either Linux or OPTEE can use the ELE, at one point in >>>> time. >>> >>> That has nothing to do with the fix. The fix is for platforms/SoCs which >>> do have 2-MUs, but you also have written that there are platforms with >>> only 1-MU. >>> >>> This MU can't be shared between secure and non-secure world. >>> >>>>> IMHO it makes much more sense to put the complete ELE communication into >>>>> (OP-)TEE and let the secure OS taking care of it. All non-secure world >>>>> requests are passed via (OP-)TEE to the ELE. This involves: >>>>> - eFuse access (done via OP-TEE i.MX specific PTA) >>>>> - ELE 23h59m ping (kernel SMC WDG driver, requires OP-TEE watchdog driver) >>>>> - HW-RNG (kernel OP-TEE HWRNG driver + OP-TEE HWRNG PTA) >>>> >>>> There is a dedicated MU "trusted-MU" for OPTEE-OS. The idea to converge to a >>> >>> Yes for systems with 2-MUs there is a "trusted-MU" and a >>> "non-trusted-MU". As of now, there is no fix available for using both >>> MUs at the same time. Furhtermore there are platforms/SoCs with only >>> 1-MU, as you have written in your commit message. This 1-MU system can >>> have the MU either trusted or non-trusted. >>> >>>> single path via OPTEE-OS, is good. But it will impact the performance of the >>>> features at Linux side. >>> >>> Performance? We are talking about a ping every 23h59m (I still don't >>> know if this is a feature or bug), eFuse write/read, and the HW-RNG >>> which can seed the Linux PRNG. >>> >>>> Since the fix is still WIP. Let's wait till then. >>> >>> The fix is for the 2-MUs SoCs but not the 1-MU case. >>> >>> I would like to have a system design which doesn't differ too much >>> between SoCs which are equipped with the ELE engine. >> >> Do we really want to depend on OP-TEE to be available for having things >> like OTP fuse access and HWRNG? Personally I'd like to be able to build >> systems with OTP access and HWRNG but without OP-TEE. Requiring OP-TEE >> only to make the ELE available to the kernel in cases where the secure >> world isn't used for anything else seems to be unnecessarily complex. > > I understand your point. I don't like pulling in more FW neither but we > need to the face the following facts: > > - OTP eFuse R/W access after doing the LOCK_DOWN fuse is no longer > possible without OP-TEE. This involves general purpose (GP) eFuses > too. We faced this limitation in a current project. Ok, interesting. Where do find information about the LOCK_DOWN fuse? I don't see it mentioned in the (Security) Reference Manual of the i.MX93. > > - With new regulations like the EU CRA I think we need some sort of > secure-enclave anyway. Probably some sort of, yes. But not necessarily in the form of TEE or TrustZone, I guess. > > - Making it optional cause more paths of potential errors e.g. by not > including the correct "secure.dtsi". Multiple paths also require more > maintain- and testing effort. IMHO I do think that one of the paths > get unmaintened at some point but we would need to keep it for > backward compatibility. > > Having one implementation eliminates this since. > > - All above points assume that the ELE-FW and -HW is capable of talking > to both world, which is not the case. As we learned NXP doesn't have > a fix for the 2-MUs ELE yet and even more important there are 1-MU > ELE-IPs. > > I do see the (minimal) drawback of having +1 FW but I think this is more > an integration problem. > Speaking of FW files, for the new i.MX9* you already have plenty fo > them: bootloader, TF-A, ele-fw, scu-fw (i.MX95). So your integation > needs to handle multiple firmware files already. Sure, but I really like to keep the complexity and therefore the number of FW files as low as possible. I'm not sure what has more weight in terms of security: shipping an additional firmware and therefore increasing the attack surface or maintaining an additional code-path. > >> Anyway, I see your point of having a single implementation for the ELE >> API in the "right" place. But as far as I know other platforms like >> STM32MP1 also implement both ways for the HWRNG, secure access via OPTEE >> and non-secure access via kernel directly. > > I'm not a STM32MP1 expert but here you have this setup with the > *-scmi.dtsi. So you have two code paths which needs to be maintained and > tested. Also if one customer of yours want to use OP-TEE you need the > integration anyway, so you (Kontron) needs to maintain multiple > configuration as well. I don't see the added value. > > I think for STM32MP1 the *-scmi.dtsi support was added later because it > required a lot effort to support it. This is not the case for the i.MX9* > series. Anyway, thanks for elaborating. Your points are all valid and basically I agree. I'm fine with either way. But I'm afraid that implementing the ELE API in OP-TEE only will cause another tremendous delay for having ELE access in the kernel, especially seeing how slow NXP seems to be working on these topics right now.
