linux-kernel - Re: [PATCH] cxl/acpi: Warn on unsupported platform config detection

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Date: Tue, 25 Jun 2024 17:45:14 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Alison Schofield <alison.schofield@...el.com>, "Fabio M. De Francesco"
	<fabio.m.de.francesco@...ux.intel.com>
CC: Davidlohr Bueso <dave@...olabs.net>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Dave Jiang <dave.jiang@...el.com>, "Vishal
 Verma" <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, "Dan
 Williams" <dan.j.williams@...el.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/acpi: Warn on unsupported platform config detection

Alison Schofield wrote:
> On Wed, Jun 19, 2024 at 02:59:41PM +0200, Fabio M. De Francesco wrote:
> 
> Fabio,
> 
> cxl/acpi does a lot of platform config work. "...unsupported platform
> config detection" gives no hint that this is about CHBS's or an eRCD.
> Please offer something more specific. Thanks.

The message specifies "mixed Virtual Host and Restricted CXL Host
hierarchy" as the conflict. The relationship between RCH and eRCDs is an
exercise for the reader, and CHBS is an ACPI detail that really should
not be emitted in an error message. So I am struggling to imagine what a
more specific error message would be without paragraphs of backstory.

All that is needed here is just enough words for when someone posts a
problem to the list that someone savvy can go "ah, you fell into this
specification hole where CXL 2.0 root port registers are difficult to
associate with an RCH config, thanks for the report now we know that
Linux needs to worry about this case".