Re: Question on DOE requirements for CXL/CDAT and CMA/SPDM

[Lukas Wunner <lukas@wunner.de>]

On Thu, Feb 23, 2023 at 01:06:47PM +0000, Brian van der Beek wrote:
> For a CXL device that support both CMA/SPDM and CXL Table Access DOE
> (CDAT) data objects, is it mandatory to have a dedicated DOE instance
> for the CMA/SPMA protocol data objects?

Yes, that follows from the requirements you quoted from the PCIe spec.


> Or is it permitted for the CMA/SPDM and CXL protocols to share a
> single DOE instance?

You'd violate the PCIe spec and depend on software to handle such
non-standard behavior gracefully.


> I am reaching out to you, as I am hoping you could provide some
> insight on the Linux CMA/SPDM implementation and whether it allows
> for a DOE instance to be shared with CXL/CDAT data objects.

The code as it currently is will allow that.


> PCI-SIG replied that the requirement of a dedicated DOE instance for
> CMA/SPDM was an intentional choice based on the idea that the software
> attached to the DOE instances would be different.

The PCISIG has published the DOE 1.1 ECN in the meantime and it
allows for concurrent use of a mailbox by different software
entities (kernel, BIOS, ...) through the use of a unique
Connection ID.  You could ask the PCISIG to revisit the spec's
protocol restriction for CMA/SPDM in light of DOE 1.1.
There's an ECR for CMA/SPDM currently under development.

Thanks,

Lukas