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Message-ID: <42f95f6a-8c92-40b3-9ad2-623ff4d8267c@amd.com>
Date: Fri, 17 Jan 2025 15:31:43 -0600
From: Ben Cheatham <benjamin.cheatham@....com>
To: Robert Richter <rrichter@....com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Gregory Price
	<gourry@...rry.net>, "Fabio M. De Francesco"
	<fabio.m.de.francesco@...ux.intel.com>, Terry Bowman <terry.bowman@....com>,
	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>
Subject: Re: [PATCH v1 15/29] cxl/region: Use an endpoint's SPA range to find
 a region

On 1/7/25 8:10 AM, 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 and use it to find the endpoint's region.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/core/region.c | 85 ++++++++++++++++++++++++++++++++-------
>  drivers/cxl/cxl.h         |  1 +
>  2 files changed, 71 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 09a68e266a79..007a2016760d 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -824,6 +824,41 @@ static int match_free_decoder(struct device *dev, void *data)
>  	return 1;
>  }
>  
> +static int cxl_port_calc_hpa(struct cxl_port *port, struct cxl_decoder *cxld,
> +			     struct range *hpa_range)
> +{
> +	struct range hpa = *hpa_range;
> +	u64 len = range_len(&hpa);
> +
> +	if (!port->to_hpa)
> +		return 0;
> +
> +	/* Translate HPA to the next upper domain. */
> +	hpa.start = port->to_hpa(cxld, hpa.start);
> +	hpa.end = port->to_hpa(cxld, hpa.end);
> +
> +	if (!hpa.start || !hpa.end ||
> +	    hpa.start == ULLONG_MAX || hpa.end == ULLONG_MAX) {
> +		dev_warn(&port->dev,
> +			"CXL address translation: HPA range invalid: %#llx-%#llx:%#llx-%#llx(%s)\n",
> +			hpa.start, hpa.end, hpa_range->start,
> +			hpa_range->end, dev_name(&cxld->dev));
> +		return -ENXIO;
> +	}
> +
> +	if (range_len(&hpa) != len * cxld->interleave_ways) {
> +		dev_warn(&port->dev,
> +			"CXL address translation: HPA range not contiguous: %#llx-%#llx:%#llx-%#llx(%s)\n",
> +			hpa.start, hpa.end, hpa_range->start,
> +			hpa_range->end, dev_name(&cxld->dev));
> +		return -ENXIO;
> +	}
> +
> +	*hpa_range = hpa;
> +
> +	return 0;
> +}
> +
>  static int match_auto_decoder(struct device *dev, void *data)
>  {
>  	struct cxl_region_params *p = data;
> @@ -3214,26 +3249,47 @@ cxl_port_find_switch_decoder(struct cxl_port *port, struct range *hpa)
>  static int cxl_endpoint_initialize(struct cxl_endpoint_decoder *cxled)
>  {
>  	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> -	struct cxl_port *iter = cxled_to_port(cxled);
> -	struct range *hpa = &cxled->cxld.hpa_range;
> +	struct cxl_port *parent, *iter = cxled_to_port(cxled);
> +	struct range hpa = cxled->cxld.hpa_range;
>  	struct cxl_decoder *cxld = &cxled->cxld;

Can cut down on the dereferencing a bit here by doing:
	struct cxl_decoder *cxld = &cxled->cxld;
	struct range hpa = cxld->hpa_range;

instead.

>  
> -	while (iter && !is_cxl_root(iter))
> -		iter = to_cxl_port(iter->dev.parent);
> -
> -	if (!iter)
> +	if (!iter || is_cxl_root(iter))
>  		return -ENXIO;
>  
> -	cxld = cxl_port_find_switch_decoder(iter, hpa);
> -	if (!cxld) {
> -		dev_err(cxlmd->dev.parent,
> -			"%s:%s no CXL window for range %#llx:%#llx\n",
> -			dev_name(&cxlmd->dev), dev_name(&cxld->dev),
> -			cxld->hpa_range.start, cxld->hpa_range.end);
> -		return -ENXIO;
> +	while (1) {
> +		parent = parent_port_of(iter);
> +
> +		if (is_cxl_endpoint(iter))
> +			cxld = &cxled->cxld;
> +		else if (!parent || parent->to_hpa)
> +			cxld = cxl_port_find_switch_decoder(iter, &hpa);
> +
> +		if (!cxld) {
> +			dev_err(cxlmd->dev.parent,
> +				"%s:%s no CXL window for range %#llx:%#llx\n",
> +				dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
> +				hpa.start, hpa.end);
> +			return -ENXIO;
> +		}
> +
> +		/* No parent means the root port was found. */
> +		if (!parent)
> +			break;
> +
> +		/* Translate HPA to the next upper memory domain. */
> +		if (cxl_port_calc_hpa(parent, cxld, &hpa))
> +			return -ENXIO;
> +
> +		iter = parent;
>  	}
>  
> +	dev_dbg(cxld->dev.parent,
> +		"%s:%s: range:%#llx-%#llx\n",
> +		dev_name(&cxled->cxld.dev), dev_name(&cxld->dev),
> +		hpa.start, hpa.end);
> +
>  	cxled->cxlrd = to_cxl_root_decoder(&cxld->dev);
> +	cxled->spa_range = hpa;
>  
>  	return 0;
>  }
> @@ -3358,7 +3414,6 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  static int cxl_endpoint_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;
> @@ -3370,7 +3425,7 @@ static int cxl_endpoint_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);
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index c04f66fe2a93..4ccb2b3b31c9 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -419,6 +419,7 @@ struct cxl_endpoint_decoder {
>  	struct cxl_decoder cxld;
>  	struct cxl_root_decoder *cxlrd;
>  	struct resource *dpa_res;
> +	struct range spa_range;
>  	resource_size_t skip;
>  	enum cxl_decoder_mode mode;
>  	enum cxl_decoder_state state;


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