linux-kernel - Re: [PATCH v1 23/29] cxl/region: Use root decoders interleaving parameters to create a region

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Message-ID: <Z4VR_8Z1Qx4E8VSS@aschofie-mobl2.lan>
Date: Mon, 13 Jan 2025 09:48:47 -0800
From: Alison Schofield <alison.schofield@...el.com>
To: Robert Richter <rrichter@....com>
Cc: 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, Gregory Price <gourry@...rry.net>,
	"Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
	Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v1 23/29] cxl/region: Use root decoders interleaving
 parameters to create a region

On Tue, Jan 07, 2025 at 03:10:09PM +0100, Robert Richter wrote:
> Endpoints requiring address translation might not be aware of the
> system's interleaving configuration. Instead, interleaving can be
> configured on an upper memory domain (from an endpoint view) and thus
> is not visible to the endpoint. For region creation this might cause
> an invalid interleaving config that does not match the CFMWS entries.
> 
> Use the interleaving configuration of the root decoders to create a
> region which bases on CFMWS entries. This always matches the system's
> interleaving configuration and is independent of the underlying memory
> topology.

This sounds like a restriction, more restrictive than present.

Won't it block all region interleave ways greater than root decoder
interleave ways? ie. disallows 2, 2+2, 2+2+2, 4, etc.


> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/core/region.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index e218f0be2409..c3322bae05b9 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3477,8 +3477,8 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  	}
>  
>  	p->res = res;
> -	p->interleave_ways = cxled->cxld.interleave_ways;
> -	p->interleave_granularity = cxled->cxld.interleave_granularity;
> +	p->interleave_ways = cxlrd->cxlsd.cxld.interleave_ways;
> +	p->interleave_granularity = cxlrd->cxlsd.cxld.interleave_granularity;
>  	p->state = CXL_CONFIG_INTERLEAVE_ACTIVE;
>  
>  	rc = sysfs_update_group(&cxlr->dev.kobj, get_cxl_region_target_group());
> -- 
> 2.39.5
>