linux-kernel - Re: [PATCH v1 16/29] cxl/region: Use translated HPA ranges to calculate the endpoint position

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Message-ID: <Z32kMmH25_qfHhZ5@gourry-fedora-PF4VCD3F>
Date: Tue, 7 Jan 2025 17:01:22 -0500
From: Gregory Price <gourry@...rry.net>
To: Robert Richter <rrichter@....com>
Cc: Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Dan Williams <dan.j.williams@...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,
	"Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
	Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v1 16/29] cxl/region: Use translated HPA ranges to
 calculate the endpoint position

On Tue, Jan 07, 2025 at 03:10:02PM +0100, Robert Richter wrote:
> To enable address translation, the calculation of the endpoint
> position must use translated HPA ranges. The function
> cxl_endpoint_initialize() already uses translation which could be
> reused to calculate the endpoint position.
> 
> Use translated HPA address ranges for the calculation of endpoint
> position by moving it to cxl_endpoint_initialize(). Create a function
> cxl_port_calc_pos() for use in the iterator there, but keep a
> simplified version of cxl_calc_interleave_pos() for the
> non-auto-discovery code path without address translation since it is
> not support there.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---

just one inline question

> +static int cxl_calc_interleave_pos(struct cxl_endpoint_decoder *cxled)
> +{
> +	struct cxl_port *iter, *port = cxled_to_port(cxled);
> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +	struct range *range = &cxled->cxld.hpa_range;
> +	int pos = 0;
> +
> +	/*
> +	 * Address translation is only supported for auto-discovery of
> +	 * decoders. There is no need to support address translation
> +	 * here.
> +	 */

Just clarifying - it's only supported for discovery of already
programmed decoders (programmed in BIOS)? i.e. driver-programmed
decoders shouldn't need this translation / won't support this type of
interleaving?

Comment here begs some questions but not necessarily a review blocker.

~Gregory