linux-kernel - Re: [PATCH v2 08/15] cxl/region: Use the endpoint's SPA range to find a region

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Message-ID: <Z7eCU3njj64GZFsJ@gourry-fedora-PF4VCD3F>
Date: Thu, 20 Feb 2025 14:28:19 -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 08/15] cxl/region: Use the endpoint's SPA range to
 find a region

On Tue, Feb 18, 2025 at 02:23:49PM +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.
> 
> Use the calculated SPA range of an endpoint to find the endpoint's
> region.
>
> Signed-off-by: Robert Richter <rrichter@....com>

May be worth noting that cxl_endpoint_initialize() will set
cxled->spa_range regardless of whether HPA=SPA or not, and so it will
always contain the correct value at this point - even if translation
was not required.

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

> ---
>  drivers/cxl/core/region.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 6d5ede5b4c43..ffe6038249ed 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3535,7 +3535,6 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  static int cxl_endpoint_decoder_add(struct cxl_endpoint_decoder *cxled)
>  {
> -	struct range *hpa = &cxled->cxld.hpa_range;
>  	struct cxl_root_decoder *cxlrd = cxled->cxlrd;
>  	struct cxl_region_params *p;
>  	struct cxl_region *cxlr;
> @@ -3547,7 +3546,7 @@ static int cxl_endpoint_decoder_add(struct cxl_endpoint_decoder *cxled)
>  	 * one does the construction and the others add to that.
>  	 */
>  	mutex_lock(&cxlrd->range_lock);
> -	cxlr = cxl_find_region_by_range(cxlrd, hpa);
> +	cxlr = cxl_find_region_by_range(cxlrd, &cxled->spa_range);
>  	if (!cxlr)
>  		cxlr = construct_region(cxlrd, cxled);
>  	mutex_unlock(&cxlrd->range_lock);
> -- 
> 2.39.5
>