Re: [PATCH] PCI/DOE: Expose the DOE protocols via sysfs

From: Alistair Francis
Date: Tue Aug 01 2023 - 10:04:40 EST

On Mon, Jul 31, 2023 at 1:52 PM Lukas Wunner <lukas@xxxxxxxxx> wrote:
> On Mon, Jul 31, 2023 at 11:30:29AM -0400, Alistair Francis wrote:
> > Yep, a big benefit is lspci or other userspace tools to be able to see
> > what DOE protocols are supported.
> Fair enough, but please make that motivation explicit in the commit
> message.

Fixed in v2

> > I also have plans to expose DOE mailboxes to userspace. That way we
> > can run the SPDM requester code (using libspdm) in userspace to
> > communicate with devices using SPDM. That will allow device
> > authentication for example.
> That duplicates our effort to bring up authentication in the kernel:

That's great!

> We had a lengthy debate on the pros and cons of doing SPDM in-kernel
> versus in user space. We realized that when resuming a device from
> D3cold or recovering it after reset, the user space component performing
> SPDM authentication might reside on the device (disk, network) being
> resumed or reset, preventing its execution.
> When resuming from system sleep, devices need to be reauthenticated
> during the ->resume_noirq phase, i.e. with device interrupts disabled,
> as drivers are allowed access to devices already in that phase.
> So authentication (and encryption establishment) needs to happen this
> early, when user space isn't available yet.

Yeah, I had the same debate. Resume/suspend and reset are good points though.

Do you plan on supporting all SPDM commands in the kernel and then
passing information to userspace as required?


> See the commit message of "PCI/CMA: Reauthenticate devices on reset
> and resume" on the above-linked branch for details.
> Thanks,
> Lukas