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

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Message-ID: <20250915112341.00000ec6@huawei.com>
Date: Mon, 15 Sep 2025 11:23:41 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
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>, Dave Jiang <dave.jiang@...el.com>, "Davidlohr
 Bueso" <dave@...olabs.net>, <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 Fri, 12 Sep 2025 16:45:04 +0200
Robert Richter <rrichter@....com> 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>
Trivial comment inline.

Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.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,
> +	};

There is DEFINE_RANGE() which you could use here
	cxlr->hpa_range = DEFINE_RANGE(0, -1);

Not sure if it is worth bothering though.



> +
>  	cxl_region_iomem_release(cxlr);
>  	p->state = CXL_CONFIG_IDLE;
> +
>  	return 0;
>  }