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

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Message-ID: <aMpuBypN42be3ruR@rric.localdomain>
Date: Wed, 17 Sep 2025 10:15:03 +0200
From: Robert Richter <rrichter@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.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 15.09.25 11:23:41, Jonathan Cameron wrote:
> 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.

It is pretty new. Given the wide range of users of DEFINE_RES_*, let's
start using this one too.

-Robert