Re: [PATCH 1/3] x86/amd_nb: Add support for HSMP mailbox access

From: Chatradhi, Naveen Krishna
Date: Wed Sep 08 2021 - 13:11:45 EST

HI Boris,

On 9/2/2021 11:28 PM, Borislav Petkov wrote:
[CAUTION: External Email]

On Thu, Sep 02, 2021 at 11:11:53PM +0530, Naveen Krishna Chatradhi wrote:
On Fam19h server CPUs from AMD an HSMP (Host System Management Port)
mailbox interface is added to monitor and manage the CPU parameters.
Mailbox? Hmm, that rings a bell. There's drivers/mailbox/ with a bunch
of drivers in there. Those are

"Mailbox is a framework to control hardware communication between
on-chip processors through queued messages and interrupt driven

I wonder if that HSMP thing can be wrapped like a mailbox driver...

Sure, I will look into the mailbox framework.

If not, I still don't like it being slapped in amd_nb.c where it would
be built in on *all* AMD hardware which is kinda too much.

In all the future server platforms, AMD's direction is the support HSMP interface, which exposes system management knobs.

You could make it a separate driver module called amd_hsmp.ko which
loads only on the appropriate hw and uses amd_nb.c for detection only
like the other drivers, for example.

How about, creating a module under drivers/platform/x86/ (lets say amd_hsmp.c) export an API from here and it can be extended to support all the knobs that does not fit in an existing frameworks (such as hwmon, etc) and provide a user space access.

I can see similar references in the drivers/platform/x86/ directory.