Re: [PATCH 0/3] arm64/virt: Add Arm CCA measurement register support

Suzuki K Poulose
2026-04-14T13:28:08Z

On 14/04/2026 13:29, Jason Gunthorpe wrote:
> On Tue, Apr 14, 2026 at 11:10:51AM +0100, Suzuki K Poulose wrote:
>
>>> Isn't this also sort of incomplete? Doesn't anything serious need
>>> signed measurements? Isnt't there alot more data that comes out of RMM
>>> than just a few measurement registers?
>> As mentioned above, this series adds the support for Runtime Extendible
>> Measurements (REM in CCA, RTMR on TDX). The RIM+Platform Attestation is
>> already provided via the TSM_REPORT
>
> Okay, but what actual use is this?
>

Good point. This REMs are planned to be used for
EFI_CC_MEASUREMENT_PROTOCOL as described below:

https://github.com/tianocore/edk2/issues/11383

At the moment they are exposed as raw, similar to the Intel TDX RTMRs.
This may eventually need to be connected to IMA subsystem.

> Extendable measrements with no log
> Measurement read back without signature
>
> What is the use case? What do you imagine any userspace will do with
> this? Put it in the cover letter.

Agreed.

>
> I don't think the raw rmm calls are sufficiently developed to be
> usable directly by userspace. They are less capable than TPM and even
> TPM has a lot of software around it to make it useful.

See above.

Kind regards
Suzuki

>
> Jason