Re: [PATCH 0/4] keys: Introduce a keys frontend for attestation reports

[Huang, Kai]

On Tue, 2023-08-08 at 11:17 -0700, Dan Williams wrote:
> Dionna Amalie Glaze wrote:
> > > 
> > > I do not see sysfs precluding a use case like that. If the kernel can
> > > call out to userspace for TLS connection setup [1], then advanced user
> > > can call out to a daemon for workload provenance setup. Recall that TDX
> > > will round trip through the quoting enclave for these reports and,
> > > without measuring, that seems to have the potential to dominate the
> > > setup time vs the communication to ask a daemon to convey a report.
> > > 
> > 
> > It's rather hard to get new daemons approved for container
> > distributions since they end up as resource hogs.
> > I really don't think it's appropriate to delegate to a daemon to
> > single-thread use of a kernel interface when the interface could
> > provide functional semantics to begin with.
> 
> That's fair, it's also not without precedence for the kernel to await a
> strong motivation of a use case before taking on a higher maintenance
> burden. Unifying kernel interfaces is important for maintainability and
> difficult / needs care. sysfs simplifies maintainability (but exports
> complexity to userspace), keyring simplifies that (but there is a valid
> argument that this is not a key), ioctl complicates that (it is not as
> amenable to transport unification as the above options).
> 

I don't quite follow why ioctl() is not amenable to transport unification as the
/sysfs?  IIUC both are new ABI(s) to the userspace thus userspace needs to adopt
anyway.  

On the other hand, ioctl() seems to be able to handle concurrent requests better
than /sysfs, if we want to support the case that integrating attestation to the
handshake protocols.