linux-kernel - Re: [PATCH v2 05/15] cxl/region: Calculate and store the SPA range of an endpoint

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Message-ID: <Z7d3fuL_YuwFWM2n@gourry-fedora-PF4VCD3F>
Date: Thu, 20 Feb 2025 13:42:06 -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 v2 05/15] cxl/region: Calculate and store the SPA range
 of an endpoint

On Tue, Feb 18, 2025 at 02:23:46PM +0100, Robert Richter wrote:
> To find the correct region and root port of an endpoint of a system
> needing address translation, the endpoint's HPA range must be
> translated to each of the parent port address ranges up to the root
> decoder.
> 
> Calculate the SPA range using the newly introduced callback function
> port->to_hpa() that translates the decoder's HPA range to its parent
> port's HPA range of the next outer memory domain. Introduce the helper
> function cxl_port_calc_hpa() for this to calculate address ranges
> using the low-level port->to_hpa() callbacks. Determine the root port
> SPA range by iterating all the ports up to the root. Store the
> endpoint's SPA range for later use.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
>  
> +	/*
> +	 * Address translation is only supported for auto-discovery of
> +	 * decoders. There is no need to support address translation
> +	 * here. That is, do not recalculate ctx.hpa_range here.
> +	 */

Can we at least add why translation is not supported / needed?  Just
saying "there is no need" doesn't help devs after us understand the code.

With that change:

Reviewed-by: Gregory Price <gourry@...rry.net>