Re: [RFC PATCH v1 06/11] PCI/TSM: Describe the PCI attestation control family

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Nov 04, 2026 at 10:21:02AM +0100, Jiri Pirko wrote:
> >If we want to do what I called option a, with user space repeat, then
> >we need a CTLV command to start the flow, not sysfs.
> >
> >I have been thinking sysfs should only create the attestation end
> >point and not do any RMM operations
> 
> Okay, sysfs connect can just associate the TSM and create the
> attestation instance. Starting/restarting the protocol would be driven
> through CTLV, Is SPDM_GET op the one you have in mind, or something
> additional done before it?

I haven't got so far as to think about good names. Will work on it

> >> SPDM_GET (attestation provider):
> >>   Return the retained discovery information and connection state.
> >>   There is no corresponding RMI discovery command.
> >
> >> EVIDENCE_GET(CERT_CHAIN, blob-instance=N):
> >>   Return the retained DER certificate chain for slot N.
> >
> >I think these two are my #2
> > 
> >> SPDM_AUTHENTICATE(device-generation, slot):
> >>   Validate the generation and selected slot.
> >>   RMI_PDEV_CREATE(id_index=slot)
> >
> >Maybe PDEV_CREATE is in my #1?
> 
> For current RMM, PDEV_CREATE fixes the certificate slot through
> id_index. For option (a), I would therefore leave it in #3:
> START is a no-op; FINISH(slot) creates the PDEV and runs to
> PDEV_READY.

Really? Yuk, I think that is a mistake, the slot should have been
on RMI_PDEV_SET_PUBKEY.

But OK, yeah I think it works OK at step #3. I was thinking that the
PDEV_CREATE should happen at sysfs time as part of creating the
attestation device. Maybe in future.

There is also a complication that we cannot destroy the PDEV while a
VDEV/VIOMMU exists so the RMM driver will have to handle this
with some refcounting. EBUSY on #3 I guess.

> >>   Prepare the root-port PDEV to READY and configure PCI IDE resources.
> >>   RMI_PDEV_STREAM_CONNECT
> >>   RMI_PDEV_COMMUNICATE on both PDEVs, honoring STREAM_WAIT
> >>   RMI_PDEV_STREAM_COMPLETE
> >>   Enable the endpoint IDE stream.
> >>   Only then publish authenticated state and the new device-generation.
> >
> >Oh is IDE under the control of the OS for RMM? I hadn't read that far
> >ahead. Then it should be done as part of the "ACCEPT" step #5
> 
> Yes, the host drives IDE setup through the RMI stream operations;
> RMM handles key management. We can move that setup to host
> EVIDENCE_ACCEPT, after appraising the session identity.

Perfect

Jason