linux-kernel - Re: [PATCH v2 3/5] cxl/acpi: Add platform flag for HPA address translation

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Message-ID: <ZpIvwsu39jC3r0Ns@rric.localdomain>
Date: Sat, 13 Jul 2024 09:41:54 +0200
From: Robert Richter <rrichter@....com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>, linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] cxl/acpi: Add platform flag for HPA address
 translation

On 11.07.24 18:27:30, Dan Williams wrote:
> Robert Richter wrote:
> > Adding an early check to detect platform specifics to (later) enable
> > HPA address translation. The cxl_root structure is used to store that
> > information.
> > 
> > Note: The platform check will be added later when enabling address
> > translation.
> 
> It feels odd to have a flag at the root for this because the translation
> is at the host-bridge level, right?
> 
> I was more thinking of a solution that does:
> 
> spa = cxld_hpa_to_spa(cxld);
> 
> ...and then internal to that the code walks the port hierarchy from it's
> host port to the host bridge. Then does something like
> 
> hb->hpa_to_spa(hb, hpa)
> 
> Where @hb is:
> 
> struct cxl_hb {
> 	struct cxl_port port;
> 	u64 (*hpa_to_spa)(struct cxl_hb *, u64);
> }

Ok, will consider that for the rework.

-Robert