Re: [RFC PATCH v1 02/11] attestation: Filter evidence objects per instance

[Jiri Pirko <jiri@resnulli.us>]

Wed, Oct 28, 2026 at 04:26:09PM +0100, aneesh.kumar@kernel.org wrote:
>Allow an attestation instance to expose only the evidence objects its
>device supports. Add an optional evidence_object_supported() callback
>and use it both when building DEVICE_GET capabilities and when checking
>EVIDENCE_GET requests.
>
>The following PCI/TSM patch uses one attestation implementation for
>devices that support different evidence objects. Its list includes
>certificate slots 0-7, SPDM VCA, measurements, and a TDISP interface
>report. Each device must expose only the objects it supports, for
>example:
>
>  Instance                  Supported evidence objects
>  ------------------------  ------------------------------------------
>  Host link using slot zero Certificate slot 0
>  CCA guest device          Certificate slot 0, VCA, measurements,
>                            TDISP interface report
>  Host PF0 after discovery  Certificate slots reported populated by SPDM
>
>PCI/TSM checks the TSM driver's evidence_types bitmap or, after SPDM
>discovery on a host PF0, the populated-slot bitmap. The preceding patch
>controls whether EVIDENCE_GET is enabled; this patch controls which
>objects that operation can retrieve.

For SPDM slots, I think it would make sense to distinguish supported
slot addresses from discovered population. DEVICE_GET describes fixed
object tuples, formats and limits; SPDM_GET reports the populated
slots and their certificate digests. An empty supported slot
returns -ENOENT.

Fixed differences between backend instances can be selected before
publication. Please do not make the capability set follow a
populated-slot bitmap that can change during the instance lifetime.

[..]