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Date:   Tue, 13 Jun 2023 09:47:43 -0700 (PDT)
From:   Shyam Saini <shyamsaini@linux.microsoft.com>
To:     "Zhu, Bing" <bing.zhu@intel.com>
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Subject: RE: [PATCH  v2 0/4] rpmb subsystem, uapi and virtio-rpmb driver
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Hi Bing,

Other than PCRs we also want to store Non volatile ftpm data (NVData), 
storing these in volatile DDR shared memory will be a spec violation.

Best Regards,
Shyam

> As an alternative, Is it possible to change ftpm design not to depend on RPMB access at the earlier/boot stage? Because to my understanding, typically PCRs don't require persistent/NV storage (for example, before RPMB or tee-supplicant is ready, use TEE memory instead as temporary storage)
>
> Bing
>
> IPAS Security Brown Belt (https://www.credly.com/badges/69ea809f-3a96-4bc7-bb2f-442c1b17af26)
> System Software Engineering
> Software and Advanced Technology Group
> Zizhu Science Park, Shanghai, China
>
> -----Original Message-----
> From: Shyam Saini <shyamsaini@linux.microsoft.com>
> Sent: Thursday, June 1, 2023 3:10 AM
> To: alex.bennee@linaro.org
> Cc: code@tyhicks.com; Matti.Moell@opensynergy.com; arnd@linaro.org; Zhu, Bing <bing.zhu@intel.com>; hmo@opensynergy.com; ilias.apalodimas@linaro.org; joakim.bech@linaro.org; linux-kernel@vger.kernel.org; linux-mmc@vger.kernel.org; linux-scsi@vger.kernel.org; maxim.uvarov@linaro.org; ruchika.gupta@linaro.org; Winkler, Tomas <tomas.winkler@intel.com>; ulf.hansson@linaro.org; Huang, Yang <yang.huang@intel.com>; sumit.garg@linaro.org; jens.wiklander@linaro.org; op-tee@lists.trustedfirmware.org
> Subject: [PATCH v2 0/4] rpmb subsystem, uapi and virtio-rpmb driver
>
> Hi Alex,
>
> [ Resending, Sorry for the noise ]
>
> Are you still working on it or planning to resubmit it ?
>
> [1] The current optee tee kernel driver implementation doesn't work when IMA is used with optee implemented ftpm.
>
> The ftpm has dependency on tee-supplicant which comes once the user space is up and running and IMA attestation happens at boot time and it requires to extend ftpm PCRs.
>
> But IMA can't use PCRs if ftpm use secure emmc RPMB partition. As optee can only access RPMB via tee-supplicant(user space). So, there should be a fast path to allow optee os to access the RPMB parititon without waiting for user-space tee supplicant.
>
> To achieve this fast path linux optee driver and mmc driver needs some work and finally it will need RPMB driver which you posted.
>
> Please let me know what's your plan on this.
>
> [1] https://optee.readthedocs.io/en/latest/architecture/secure_storage.html
>
> Best Regards,
> Shyam
>