Re: [PATCH 0/4] tsm: Unified Measurement Register ABI for TVMs

[Xing, Cedric]

On 2/13/2025 10:58 AM, Dave Hansen wrote:
> On 2/13/25 08:21, Xing, Cedric wrote:
> > On 2/12/2025 10:50 PM, Dave Hansen wrote:
> > > On 2/12/25 18:23, Cedric Xing wrote:
> > > > NOTE: This patch series introduces the Measurement Register (MR) ABI,
> > > > and
> > > > is a continuation of the RFC series on the same topic [1].
> > >
> > > Could you please explain how the benefits of this series are helpful to
> > > end users?
> >
> > This series exposes MRs as sysfs attributes, allowing end users to
> > access them effortlessly without needing to write any code. This
> > simplifies the process of debugging and diagnosing measurement-related
> > issues. Additionally, it makes the CC architecture more intuitive for
> > newcomers.
>
> Wait a sec, so there's already ABI for manipulating these? This just
> adds a parallel sysfs interface to the existing ABI?
No, this is new. There's no existing ABI for accessing measurement 
registers from within a TVM (TEE VM). Currently, on TDX for example, 
reading TDX measurement registers (MRs) must be done by getting a TD 
quote. And there's no way to extend any RTMRs. Therefore, it would be 
much easier end users to debug/diagnose measurement related issues 
(which would almost always require reading MRs) with this patch.

> Also, you're saying that users don't need to write any code, but then
> provide... sample code. That's unexpected.
The sample code is to demo how to expose MRs from a CC guest driver, but 
not for end users to access those MRs.

> Oh, and you seem to have forgotten to attach the sysfs ABI documentation
> patch to the series. You did write the required documentation, right? ;)
Documentation/ABI/testing/sysfs-kernel-tsm (new file added by patch 1) 
contains a description on the attributes added by the patch.