Re: [RFC Part2 PATCH v3 02/26] crypto: ccp: Add Platform Security Processor (PSP) device support

[Brijesh Singh]

On 09/08/2017 03:40 AM, Borislav Petkov wrote:
> On Thu, Sep 07, 2017 at 05:19:32PM -0500, Brijesh Singh wrote:
> > At high level, AMD-SP (AMD Secure Processor) (i.e CCP driver) will provide the
> > support for CCP, SEV and TEE FW commands.
> >
> >
> >           +--- CCP
> >           |
> > AMD-SP --|
> >           |            +--- SEV
> >           |            |
> >           +---- PSP ---*
> >                        |
> >                        +---- TEE
>
> I still don't see the need for such finegrained separation, though.
> There's no "this is a separate compilation unit because... ". At least
> the PSP branch could be a single driver without the interface.
>
> For example, psp_request_sev_irq() is called only by sev_dev_init(). So
> why is sev-dev a separate compilation unit? Is anything else going to
> use the PSP interface?


I don't know anything about the TEE support hence I don't have very strong
reason for finegrained separation -- I just wanted to ensure that the SEV
enablement does not interfere with TEE support in the future.


> If not, just put it all in a psp-dev file and that's it. We have a
> gazillion config options and having two more just because, is not a good
> reason. You can always carve it out later if there's real need. But if
> the SEV thing can't function without the PSP thing, then you can just as
> well put it inside it.
>
> This way you can save yourself a bunch of exported functions and the
> like.
>
> Another example for not optimal design is psp_request_tee_irq() - it
> doesn't really request an irq by calling into the IRQ core but simply
> assigns a handler. Which looks to me like you're simulating an interface
> where one is not really needed. Ditto for the sev_irq version, btw.


It's possible that both TEE and SEV share the same interrupt but their
interrupt handling approach could be totally different hence I tried to
abstract it.

I am making several assumption on TEE side without knowing in detail

I can go with your recommendation -- we can always crave it out later once
the TEE support is visible.

-Brijesh