Re: [PATCH RFC 00/20] attestation: Add a common subsystem and TDX support

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 23 Oct 2026 12:42:12 -0300
Jason Gunthorpe <jgg@ziepe.ca> wrote:

> On Fri, Oct 23, 2026 at 08:58:35PM +0530, Aneesh Kumar K.V wrote:
> > Jason Gunthorpe <jgg@ziepe.ca> writes:
> >   
> > > On Fri, Oct 23, 2026 at 01:34:53PM +0530, Aneesh Kumar K.V wrote:
> > >  
> > >> CCA currently takes the device identity index during pdev_create. I am
> > >> investigating how to retrieve the certificate chains for all slots. For
> > >> now, I have implemented the sequence below.  
> > >
> > > Yeah, I think the consensus at LPC was this may be a gap in CCA.  
> > 
> > I checked with Alexey, and if I understand him correctly, TIO also needs
> > to establish eight separate connections to retrieve the certificate
> > chains.  
> 
> Lovely!
> 
> > For now, I am trying Jiri's suggestion: use Rust SPDM to fetch the
> > certificate chain and return it via evidence-get. evidence-accept then
> > does pdev-create with the specified slot number and compares the
> > evidence data returned by the RMM with the value cached by Rust SPDM. If
> > they match, it uses the cached value for set_pub_key. This seems to be
> > working. (FVP only supports slot 0, hence only one blob-instance)  
> 
> That's a pretty good idea, and works for every arch! Maybe that is
> the best long term direction.

We discussed doing similar a long time back..  As long as
we use the DOE before the TSM gets hold of it we can have any
conversation we like with the device.

At the time the idea was do the full flow native and if the host
was happy with what it saw, then it could decide to let the TSM
have a play.  The lesser step here (IIUC) is just grab the certs
(so first chunk of typical SPDM flow) seems enough for now
as only a config picking step.

Sounds good to me.

...

> 
> It certainly seems like it should be all sketched out and the uAPI
> confirmed. Given the state of things I don't see an issue with a slot
> 0 only initial configuration (ie EOPNOTSUPP the certificate gets) so
> long as the long term resolution is clear.

Agreed - baby steps is fine.

Jonathan