linux-kernel - Re: [PATCH v3 02/11] cxl/region: Store HPA range in struct cxl

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Message-ID: <fd4fc0f6-03a9-4134-9703-60705ec6898c@intel.com>
Date: Fri, 12 Sep 2025 10:17:14 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Robert Richter <rrichter@....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>,
 Davidlohr Bueso <dave@...olabs.net>
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>, Joshua Hahn <joshua.hahnjy@...il.com>
Subject: Re: [PATCH v3 02/11] cxl/region: Store HPA range in struct cxl_region



On 9/12/25 7:45 AM, Robert Richter wrote:
> Each region has a known host physical address (HPA) range it is
> assigned to. Endpoint decoders assigned to a region share the same HPA
> range. The region's address range is the system's physical address
> (SPA) range.
> 
> Endpoint decoders in systems that need address translation use HPAs
> which are not SPAs. To make the SPA range accessible to the endpoint
> decoders, store and track the region's SPA range in struct cxl_region.
> Introduce the @hpa_range member to the struct. Now, the SPA range of
> an endpoint decoder can be determined based on its assigned region.
> 
> Patch is a prerequisite to implement address translation which uses
> struct cxl_region to store all relevant region and interleaving
> parameters.
> 
> Signed-off-by: Robert Richter <rrichter@....com>

Just a nit below. Otherwise looks ok

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> ---
>  drivers/cxl/core/region.c | 17 +++++++++++++++++
>  drivers/cxl/cxl.h         |  2 ++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 2c37c060d983..777d04870180 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -664,6 +664,11 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
>  		return PTR_ERR(res);
>  	}
>  
> +	cxlr->hpa_range = (struct range) {
> +		.start = res->start,
> +		.end = res->end,
> +	};
> +
>  	p->res = res;
>  	p->state = CXL_CONFIG_INTERLEAVE_ACTIVE;
>  
> @@ -700,8 +705,14 @@ static int free_hpa(struct cxl_region *cxlr)
>  	if (p->state >= CXL_CONFIG_ACTIVE)
>  		return -EBUSY;
>  
> +	cxlr->hpa_range = (struct range) {
> +		.start = 0,
> +		.end = -1,
> +	};
> +
>  	cxl_region_iomem_release(cxlr);
>  	p->state = CXL_CONFIG_IDLE;
> +

stray blank line
>  	return 0;
>  }
>  
> @@ -2400,6 +2411,11 @@ static void unregister_region(void *_cxlr)
>  	for (i = 0; i < p->interleave_ways; i++)
>  		detach_target(cxlr, i);
>  
> +	cxlr->hpa_range = (struct range) {
> +		.start = 0,
> +		.end = -1,
> +	};
> +
>  	cxl_region_iomem_release(cxlr);
>  	put_device(&cxlr->dev);
>  }
> @@ -3458,6 +3474,7 @@ static int __construct_region(struct cxl_region *cxlr,
>  	}
>  
>  	set_bit(CXL_REGION_F_AUTO, &cxlr->flags);
> +	cxlr->hpa_range = *hpa;
>  
>  	res = kmalloc(sizeof(*res), GFP_KERNEL);
>  	if (!res)
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 350ccd6949b3..f182982f1c14 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -518,6 +518,7 @@ enum cxl_partition_mode {
>   * @dev: This region's device
>   * @id: This region's id. Id is globally unique across all regions
>   * @cxlrd: Region's root decoder
> + * @hpa_range: Address range occupied by the region
>   * @mode: Operational mode of the mapped capacity
>   * @type: Endpoint decoder target type
>   * @cxl_nvb: nvdimm bridge for coordinating @cxlr_pmem setup / shutdown
> @@ -532,6 +533,7 @@ struct cxl_region {
>  	struct device dev;
>  	int id;
>  	struct cxl_root_decoder *cxlrd;
> +	struct range hpa_range;
>  	enum cxl_partition_mode mode;
>  	enum cxl_decoder_type type;
>  	struct cxl_nvdimm_bridge *cxl_nvb;